Hi,
Since you mention that the behavior is seen in other clients the cause seems to be somewhere in the connection between the parties.
Some practical info to add to your post and some tips on how to request support:
However since the behavior is also seen on Android (I presume you use them form the same network?) this leads me to conclude the issue you are experiencing is not caused by specific software on your devices and this forum would be the wrong place to request support for your issue.
For reference I use Evolution & Android have 2 gmail accounts and do not experience the issues you describe.