cAP ac can't be downgraded to bugfix (6.40.8)

RouterOS General
1

I bought cAP ac with 6.42.3 (current release).
I can not downgrade to 6.40.8 bugfix or 6.40 and got the message from log “system,error omitting package routeros-arm-6.40: min RouterOS version is 6.41”

Last week I bought wAP ac with 6.41.x and I did this steps:
6.41.x => downgrade 6.39.2 => upgrade 6.40.8
I have done it with wAP ac but not cAP ac.

I know that the architectures are different.
But the standard operation should be the same.

2

AFAIK cAP ac is quite new product and wouldn’t catch me surprised if there are missing drivers in ROS older than 6.41. Which is clearly stated as minimum version that can be installed on that device.