v1.2.3 MTU changes from 1700 to ­~670

a v1.2.3. station and ap are connected.

From time to time we lose connectivity to the STATION (reboot helps for a short while).

STA responds via Management in vlan the same way as the Data vlan.
During these time-outs no packets were lost on 32 bytes.

This is really critical as we cannot use the link at all.

After reboot the STA will respond with 1472, if we try to send customer data or access the management it goes back to about ­~670MTU. :[

[admin@agnis_maja] | ping address= do-not-fragment size=669
HOST SIZE TTL TIME STATUS timeout timeout timeout timeout timeout
sent=5 received=0 packet-loss=100%

[admin@agnis_maja] | ping address= do-not-fragment size=668
HOST SIZE TTL TIME STATUS 668 64 49ms timeout 668 64 48ms 668 64 16ms 668 64 16ms
sent=5 received=4 packet-loss=20% min-rtt=16ms avg-rtt=32ms max-rtt=49ms

[admin@agnis_maja] | ping address= do-not-fragment size=667
HOST SIZE TTL TIME STATUS 667 64 49ms timeout timeout 667 64 19ms 667 64 16ms 667 64 46ms 667 64 16ms
sent=7 received=5 packet-loss=28% min-rtt=16ms avg-rtt=29ms max-rtt=49ms

[admin@agnis_maja] | ping address= do-not-fragment size=666
HOST SIZE TTL TIME STATUS 666 64 79ms 666 64 46ms timeout timeout timeout 666 64 20ms
sent=6 received=3 packet-loss=50% min-rtt=20ms avg-rtt=48ms max-rtt=79ms

admin@agnis_maja] | ping address= do-not-fragment size=665
HOST SIZE TTL TIME STATUS 665 64 46ms 665 64 16ms 665 64 16ms 665 64 16ms 665 64 19ms
sent=5 received=5 packet-loss=0% min-rtt=16ms avg-rtt=22ms max-rtt=46ms

the same with version 1.3.4

Janis - Without understanding your network’s configuration, we may not be able to assist you correctly. We would like to troubleshoot this for you. Please contact Cambium by mailing support@cambiumnetworks.com or calling the Support phone number (http://www.cambiumnetworks.com/support/contact-support)

ok, thanks.
I’ll write an email to support with diagrams and everything.