Issue upgradin from 3.20 to 3.30

RouterOS General
1

We are currently upgrading to 3.30 from 3.20 and a few of them we have had to have customer reboot to get them to come back. has any one else seen this we have upgraded about 150 clients and have had about 10 not come back with out reboot any ideas.

our cpes are a mixture of
crossroad
133c
411

2

Is it possible to get any console output, when the problem is on the router?

3

no these are all remote routers that are on roofs have not been able to replicate in lab