Why gmail android app stops syncing on an approximately 2-3 monthly basis?

I know, this is a decades old question, answered on million sites, still none of this Q/A's match my case: I regularly have to delete the storage of the gmail app on my android (9.0-pie) device in order to regain automatic syncing of incoming emails. The internal storage is about 42% full (of 64Gb), the SD-card is 20% occupied (of 128Gb, although this is irrelevant I think), the gmail apps data storage is slightly above 64Mb (right now). In such cases neither restarting of the device, nor updating the gmail app, nor deleting the app's cached data does not help, only deleting the app's occupied storage, which does not seem to be too much (64Mb is next to nothing) to mean a real limitation. Any idea please ?