SendForEachMulticast in scheduled cloud function mostly failing

[habitoti]

Hi,

I have a scheduled cloud function that collects nightly a bunch of turn reminders for my game to be sent as push notifications. It returns an array of promises, each executing SendForEachMulticast (v1) to all the tokens of the devices a player owns. This produces usually around 40 promises being returned. Rarely all of them execute properly, sometimes just a few (maybe 1-3), most often however none at all (all tokens are registered & valid!). They all end up in timeout of 15secs then.

I only lately noted that this seems to be an issue now. It worked always properly a few month (actually years) ago . Is there any new restriction on push notifications being sent from a scheduled function? Is there any better way of making sure that those notifications are sent properly once a night? I am sending much more notifications (with actually the exact same sending code & tokens) around the clock on Realtime-DB changes, and never see any error there.

Thanks for any hints,

    habitoti