Watchlist numbering broken

When I try to edit my main watchlist, the numbering is broken (eg, several dozen entries titled as entry "1", and final entry is labelled entry "3,587", even though the list's header correctly says the list only has 3,526 entries), and any changes I try to make, just result in seemingly random changes.

It seems to be the same (or similar) issue to the one described here

https://community-imdb.sprinklr.com/conversations/imdbcom/watchlist-numbering-broken/64c9a4046f817c2d94a3cf6e

This is MY list, affected by the issue

https://www.imdb.com/list/ls089157515

thanks