Syncing issues in 2.1.x

[jonathanstegall]

Describe the bug Several users have reported issues with pushing and pulling data. I haven't been able to reproduce any of them, but should try to test as many scenarios as possible, hopefully reproduce them, and figure out what the fixes are. At least most of these users have been able to revert to 2.0.3 and fix whatever the issues are.

Problems we can confirm/reproduce

Issues will be listed in this section if we can reproduce them. If the checkbox is checked, they've been fixed by a pull request.

• [x] in PHP versions older than 7.4, there are activation errors. Reported here. Fixed in #451.
• [x] When pushing an update from a WordPress record to a Salesforce one, there can be a false positive value for the transient that detects whether it is pulling. If this happens, it will incorrectly prevent the record from pushing. Reported here. Fixed in #454.
• [x] This is more vague, but my guess is that it's also related to the above fix. Reported here
• [x] I believe this one is also related to the above fix. Reported here
• [x] Same. Reported here

Marking the ones that I believe are fixed as fixed, but will unfix if that proves to be the case after 2.1.2 is released.

Problems we need to confirm/reproduce

Issues should be listed here if they need work to reproduce in a local environment.

• [x] Reported: https://wordpress.org/support/topic/sync-loops-constant-update-pulls/ (this one was not ultimately related to 2.1.x)
• [ ] Reported: https://wordpress.org/support/topic/salesforce-no-longer-receiving-custom-fields/ (it's not clear if this is related to 2.1.x or not)

[jonathanstegall]

Closing this issue for now. If necessary, will reopen it for another version.