In case anyone else runs into the same issue, here is the response: The server is timing out before it finishes saving the batch. Instead of saving all records at the same time, we batch them into 25 so that servers can finish processing them before moving on to the next batch.
On some hosts, 25 is still too high and the batches need to be smaller so they can complete successfully before the web browser gives up and stops waiting (throwing an error).
To adjust the batch size perform the following steps:
1. Log into your FTP site and edit wp-config.php
2. Edit wp-config.php and scroll to the end and add the following bit of code:
Scroll towards the bottom, and before the line that says “Happy blogging.” add this code ABOVE that line (translate as needed):
define( 'PWBE_SAVE_BATCH_SIZE', 5 );
/* That's all, stop editing! Happy blogging. */
3. Save the wp-config.php file and re-upload it to your server.
Adjust the value until you find the sweet spot where it doesn’t timeout. A batch size of 1 will save each field one after the other.
I’m marking this thread as Resolved, since you contacted us via email as well we can continue to communicate there in case you need further assistance.