@Ferrograph - so sorry, I not see your answer and I not Give additional help.
What is your current status with latest 027 firmware, problem is still exist ?
You use one of a watchdog to monitor&fix that problem by scripting ?
Similar cases are: Chateau LTE12 - dropping LTE interface/connection - MikroTik and LTE operator problem? - I think all are about the same case with 027.