It is not possible to set a higher mtu value of 1504 on the sfp1 port in combination with a S+RJ10 and a CCR1036 8G 2S+
Two CCR directly connected with a ethernet cable (3 meter) on a SFP1 port with module S+RJ10 can not go higher than 1504 mtu value
MTU Values greater than 1504 dont work
Same problem
I open a support ticket
Reply from support:
The maximum supported MTU in S+RJ10 modules is 1504 bytes and it cannot be changed by software.
Best regards,
Janis B.
no hope 
reply from support
Hello,
It seems that you have discovered a bug, the bug does not allow you to set MTU higher than 1504. We will try to fix this as soon as possible.
Sadly for now there is no workaround for this issue.
Sorry for the inconvenience!
Best regards,
Arturs Z.
Janis said
“cannot be changed”
Arturs said
“We will try to fix this as soon as possible”
Find an Agreement! 
A fix will or will not be possible?