I have that problems with firmware 020, 022 as normal.
024 was the best but this is a beta firmware.
025 currently have got similar behavior and you are confirm that.
My way to just push that problem is put sxtr at floor or inside metal trash (empty 
) to do worse signal and when he generate 2 timeout then he stuck in offline - this is still at 025 but only when you use CellLock feature.
Additional many person report me that they have a breakes 2-6s because that 025 very like change and search better band/ca to stay connected and produce short breakes. Mostly you see that at Zoom session :).
Additional ppl say that 025 have problems with CA, they must resign from CellLock and only at*cell=0 do short breake and ca cameback (with speed).
At Chateau is the same but then a scan via 5s fix that, maybe lte modules have the same OS/RTOS perhapse but still this is like common problem in MikroTik as Vendor.
I see that you have good parameters at B3 and please read this: http://forum.mikrotik.com/t/v6-46-1-stable-is-released/135478/1
Please add a watchdog (LteLogger2) script to monitor changes at status of LTE: http://forum.mikrotik.com/t/sxt-lte-4g-cat6/134468/1
About detect the problem and triger some fix action you can discover two ways:
Simple watchdog: http://forum.mikrotik.com/t/sxt-lte-4g-cat6/134468/1
Advance watchdog: http://forum.mikrotik.com/t/tx-rx-fp-rx-dropped-pppoe-account/132656/1