Error: shard <num>: short write

Hi, I’m a newbie so sorry for possible inaccuracies in my question.

I’m using InfluxDB v1.8.3 and everything was fine before Christmas but after holidays the error in the title (“shard : short write”) appeared every time I tried to manage my db, when I tried to insert new data, to drop a measurement… I apparently fixed it switching from tsi1 to inmem (following instructions here: Upgrade to InfluxDB 1.8.x | InfluxDB OSS 1.8 Documentation) and everything works fine now but I’m not sure this really was the problem, what could have caused it?

Furthermore, searching for info about shards I’ve read here Simplifying InfluxDB: Shards and Retention Policies | InfluxData that infinite retention policy doesn’t really mean data are kept in memory endlessly but for the shard group duration (“If your retention policy is on autogen (or infinite), the data is not actually stored infinitely—this just means the retention policy matches the shard group duration, so the retention policy is effectively disabled.”) even if I can’t find a proof about that in the documentation. Is it correct?

Thank you in advance.