Invalid event after edit of single recurrence

[Terrance]

I have a long-life recurring event (every weekday since 2022), with a significant number of per-recurrence edits and deletions (~200) mostly done through Etar (via DAVx5).

The most recent edit to a recurrence resulted in an event that wouldn't sync to the server (Radicale), which was returning a 400 Bad Request and logging the following:

[WARNING] Bad PUT request on '/user/742c7347-ca22-4400-87cf-bc13d293a8a3/2fdd21ee-3b9e-45c6-bb72-da7cf442a629.ics': Overwritten recurrence with RRULESET

(see also: Kozea/Radicale#1264, Kozea/Radicale#1344)

From reading those, it seems that Etar as the iCalendar client is likely the one at fault here.

Unfortunately I don't have a copy of the iCalendar file in its broken state, but the "stable" server copy looks something like this:

📎 2fdd21ee-3b9e-45c6-bb72-da7cf442a629.sample.ics

Once in this state, I could only resolve it by unsyncing and resyncing the calendar in DAVx5. I have seen this once before, and resolved it similarly in the past. After syncing back up, making the same edit again did successfully go through.