Only wildcard masks can change to be a non-consecutive bit pattern.
Subnet masks need a mask with consecutive bits:
valid binary subnet mask:
11111111.11111111.1111111.00000000
invalid subnet mask:
01010101.11010111.1111111.01111000
You have 255.255.108.0
Which is:
11111111.11111111.01101100.0000000
Correct mask for a /17 network is:
255.255.128.0
Probably just a minor typo.