SUMMARY/TLDR: Instead of exporting directly from Whatsapp to Dropbox via "Save to Dropbox", choose "Save to Files". This option should be available for those with iOS 11, and have added their Dropbox account to the build-in Files app.
BORING BACKGROUND (skip this part if you want): It is easy and simple to export Whatsapp chats in the form of a ZIP file contain the various media and the chat text file to Dropbox. This is done by going to the chat itself, and tapping on the chat name at the top to bring up the "Contact Info" page. At the bottom of the page, there is the option to "Export Chat". A dialogue selection appears where one can select to include media or not. Depending on the size of the chat and the speed of the phone, it might take a while for Whatsapp to consolidate the data and compress it for export. When it is ready, a second dialogue box appears with two rows. The bottom row is the important one here, as it has various functions. For those who have already installed the latest Dropbox app, there should be the option to "Save to Dropbox". If this is not available, select "More..." to enable it. Upon selecting this option and then selecting the destination folder, Whatsapp will take some time to upload the file to Dropbox. Usually, this part should be longer than the consolidation process above.
PROBLEM AND SOLUTION: However, for chats (including the attached media) above 200MB, it is possible that one would receive an error message saying that Dropbox was unable to send it to Dropbox. I suppose the reason is because there is a file size limit between what Whatsapp can send directly to Dropbox. The solution is quite simple. iOS 11 came out with a new file management platform, which users can interact with via the built-in Files app. Therefore, instead of calling up Dropbox directly, Whatsapp could simply let iOS 11 handle the file transfer to Dropbox. I am not sure if this method has a file size limit, but I tried it with files of around 500MB. Ensure that the Dropbox account has been added to the Files app. Then repeat the export process on Whatsapp. At the final dialogue box, instead of selecting "Save to Dropbox", opt to "Save to Files". If the option is not available, select "More..." to enable it.
The unsettling thing is that no progress bar or confirmation will appear on Whatsapp, because it has handed the manual upload process to the File app. As far as I can tell, neither the File app nor the Dropbox app will show a progress bar either, except in the following situation. If the user has opted to automatically upload photos on the camera roll to Dropbox, and there are photos queued up to upload, then Whatsapp manual upload takes precedence. In that case, go to the Dropbox app, where the progress bar should be shown at the top under the "Photos" tab. It's a shame that the upload status page cannot be called up except under this scenario. The design concept of hiding-everything-under-the-hood has been carried out so far that many iOS apps are so poorly designed nowadays. If the progress bar cannot be seen, be patient. Even with a good connection (WiFi, broadband, etc) it can take 5-10 minutes to upload several hundred MBs. For some reason, the process is slower than a direct upload. Eventually, the export file can be found in Dropbox. Good luck.
BORING BACKGROUND (skip this part if you want): It is easy and simple to export Whatsapp chats in the form of a ZIP file contain the various media and the chat text file to Dropbox. This is done by going to the chat itself, and tapping on the chat name at the top to bring up the "Contact Info" page. At the bottom of the page, there is the option to "Export Chat". A dialogue selection appears where one can select to include media or not. Depending on the size of the chat and the speed of the phone, it might take a while for Whatsapp to consolidate the data and compress it for export. When it is ready, a second dialogue box appears with two rows. The bottom row is the important one here, as it has various functions. For those who have already installed the latest Dropbox app, there should be the option to "Save to Dropbox". If this is not available, select "More..." to enable it. Upon selecting this option and then selecting the destination folder, Whatsapp will take some time to upload the file to Dropbox. Usually, this part should be longer than the consolidation process above.
PROBLEM AND SOLUTION: However, for chats (including the attached media) above 200MB, it is possible that one would receive an error message saying that Dropbox was unable to send it to Dropbox. I suppose the reason is because there is a file size limit between what Whatsapp can send directly to Dropbox. The solution is quite simple. iOS 11 came out with a new file management platform, which users can interact with via the built-in Files app. Therefore, instead of calling up Dropbox directly, Whatsapp could simply let iOS 11 handle the file transfer to Dropbox. I am not sure if this method has a file size limit, but I tried it with files of around 500MB. Ensure that the Dropbox account has been added to the Files app. Then repeat the export process on Whatsapp. At the final dialogue box, instead of selecting "Save to Dropbox", opt to "Save to Files". If the option is not available, select "More..." to enable it.
The unsettling thing is that no progress bar or confirmation will appear on Whatsapp, because it has handed the manual upload process to the File app. As far as I can tell, neither the File app nor the Dropbox app will show a progress bar either, except in the following situation. If the user has opted to automatically upload photos on the camera roll to Dropbox, and there are photos queued up to upload, then Whatsapp manual upload takes precedence. In that case, go to the Dropbox app, where the progress bar should be shown at the top under the "Photos" tab. It's a shame that the upload status page cannot be called up except under this scenario. The design concept of hiding-everything-under-the-hood has been carried out so far that many iOS apps are so poorly designed nowadays. If the progress bar cannot be seen, be patient. Even with a good connection (WiFi, broadband, etc) it can take 5-10 minutes to upload several hundred MBs. For some reason, the process is slower than a direct upload. Eventually, the export file can be found in Dropbox. Good luck.