We're on 4.7.3 on Drupal 7, and are being affected by some bugs that affect contributions made on behalf of an organisation and paid for by paypal.
When I attempt the upgrade to 4.7.5, the upgrade script says it has updated to 4.7.4 without problems, but then hangs on Begin upgrade to 4.7.5 message
I left it for 5 minutes (the php max runtime was set to 3 minutes) and then hit refresh, it emptied - no text or progress. Re-opening the upgrade script then says it failed the integrity check. I've rolled back to a backup for now.
There is no error in the HTTP error log, nothing seems to have run out of memory.
I'd be grateful for any help in how to set about diagnosing this issue!