Reminders does not sync to iPhone SE

For several years (yes, years) I’ve been having problems with the Reminders app. The problems are largely confined to my iPhone, both on my previous phone (iPhone 6s) and my current phone (iPhone SE 2020, running iOS 16.3.1). Reminders runs extremely slowly on my phone and will not sync properly with iCloud. I've suffered from these issues (with varying degrees of severity) since the initial Reminders upgrade back in iOS 13.

I also use Reminders on my iPad (iPad Air 5th generation, running iPadOS 16.3.1) and Mac Mini (2020, running macOS Ventura 13.2.1), and though there are occasional times where one or the other is slow to sync, I rarely have to wait more than 15 minutes for the updated/added/completed reminders to be reflected on iCloud.com, and it typically happens in less than a minute.

I’ve tried all the tricks to get Reminders to work on my phone. I’ve deleted and reinstalled the app. I’ve disconnected it from iCloud, waited a couple of days, and reconnected it to iCloud. The last time I did the latter, after 48 hours it still had not completely downloaded all my reminders/lists from iCloud, so I gave up and disconnected it again. In the past, once it has completed syncing, it never again syncs. Changes to reminders made on the phone stay on the phone and do not upload to iCloud (nor do any changes in iCloud ever come down to the phone again), even though the “sync” wheel in the app suggests it is trying to sync. That wheel spins for a few hours then appears to give up, without a sync having been made. I do not believe storage space is the issue -- I am using 43.7 GB of the 64 GB on my iPhone.

On my phone I currently use Reminders only to track some tasks attached to an Outlook email address that I use in Microsoft’s To Do app. That syncs immediately and flawlessly. Interestingly, though I have only a scant few reminders in To Do, the Reminders Documents & Data size on my phone is very large (2.5 GB). See the following images:

For comparison, here is the same information from my iPad, which is actively syncing with iCloud and the large number of iCloud reminders I have there. This data is taking up only 1.34 GB on my iPad:

If anyone has any suggestions for how to get Reminders working properly on my iPhone, I’m all ears. Happy to provide any additional information that could be of help.