winbox disconnected after 20 seconds ?

Hello ,
I have notice that if I open Winbox to a rotuer version 6.46
and keep it open with out any intercation from me - it get disconnected after ~ 20 seconds
what could be the reason
when I ipen the same winbox in the same computer to version 6.42 - it can be open for hours
?
** nothing on the firewall rules on both devices …
Thanks,

Have you tried using a different version of Winbox? Are the results the same?

yes
using 2.2.15
3.11
3.18

same problem in all of them

Winbox disconnected due to heavy traffic, have you added rules to allow Winbox connections?