iQuery Connectivity timeout
When the network is unstable, there will be an alarm to leave the synchronization group. What is the timeout
Look at the "BIG-IP monitor settings" as this is the monitor that uses iquery for checking F5 devices and gatherig statistics from the LTM devices about the availability of their VIP. As a note the probe timeout for the dns/gtm big-ip monitor is 3 seconds and it was cofigurable in older versions but in newer it is not as 3 seconds is plently of time for the other F5 device to return reply to a probe request.
https://support.f5.com/csp/article/K5431
https://techdocs.f5.com/kb/en-us/products/big-ip-dns/manuals/product/bigip-dns-monitors-reference-12-1-0/3.html#unique_827581632
https://support.f5.com/csp/article/K15408
A|so check the tool iqdump for investigating issues:
https://support.f5.com/csp/article/K13690
https://support.f5.com/csp/article/K19451442