Not sure, really. It's recently been noticed by yourself and another user, and I have posted to the general Friendica support forum about it last night. Hopefully one of the devs will be able to help get things sorted.

Hey @Sergey Ivanov - do you know which date(s) the disappearing posts were from? (Even if they were, say, before a certain date, or between certain dates?)

I'm not sure which dates but I only signed up recently, probably less than a month ago. My posts started disappearing kind of randomly, the older posts.

@Adam Clark

I've been noticing comments on prior comments I made but the prior comment is often gone. I checked settings and had nothing in the basic expire post time... BUT... when I clicked advanced expiration I saw things were on by default. I turned them all off and will monitor to see if my posts are expiring anymore.

It will be interesting to see if anyone loses any further content with those advanced settings off. I'll be disabling it myself to see what happens.

@Adam Clark Since turning off the advanced expiration settings I don't seem to be losing any more posts.