mobs disappear

good day my problem is that I have mobs that I have put a name tag on I have fed and raised them, although they are completely enclosed in glass they disappear from one moment to another it's a problem I have with all kinds of mob for example a vindicator a witch a fox an ocelot sheep Polar Bear pillager and when I replace them they disappear again, I hope for an effective solution and not that they take it as a duplicate and I forgot it, that's why it is a private problem