LtAP - on LTE interface traffic drops to 0 after a few hours

Hello, I have the LtAP with two miniPCIe modems installed on boat.
On both modems I am using Vodafone CZ sim cards, but the boat is outside of CZ, so both modems work in roaming. Signal is fine here.
After some hours, internet stops working, and I see that Rx rate on LTE interface drops to 0 (see the attached screen)

  • routerOS version is upgraded to 7.9, both modems firmware is upgraded to V035 (the same behaviour was before upgrade)
  • I tried to change postrouting new-ttl to 65 as manual reccomends, but does not helped
  • this behaviour does not depend if both modems are enabled, or one only is enabled
  • this behaviour does not depend on signal strength - it will happen even with a very strong signal
    Only one method helps me (I have made it hundred times) - disable and after some seconds re-enable the LTE interface

Thank you for help or additional questions!!!

 /interface lte monitor lte1 once     
           pin-status: ok
  registration-status: roaming
        functionality: full
         manufacturer: "MikroTik"
                model: "R11e-LTE6"
             revision: R11e-LTE6_V035
     current-operator: vodafone GR
              roaming: yes
                  lac: 3073
       current-cellid: 2644992
               enb-id: 10332
            sector-id: 0
           phy-cellid: 109
    access-technology: LTE
       session-uptime: 7h7m52s
                 imei: 356662101346226
                 imsi: 230030091042636
                 uicc: 8942031015352426361
         primary-band: B7@20Mhz earfcn: 2850 phy-cellid: 109
                 rssi: -59dBm
                 rsrp: -89dBm
                 rsrq: -10dB
                 sinr: 13dB

lte1.png

Can you consider to upgrade to 7.11.2 (quite a bit of LTE changes from 7.9 to 7.11.2) and also make sure your LTE modems have the latest firmware ?