You are talking about the fact you are using a customized Windows 7 Pro x64 SP1 as OS ... how long did you create it ? This is maybe the source of the problem.
If you used EX-70 (before v22.214.171.124) to create it, there are some troubles with those old builds, and recreate your customized OS with a newer EX70, v126.96.36.199 or newer build, version should solve your trouble because I fixed the bug few builds ago.
If may try to recreate a new customized ISO, and test it in a virtual machine.
EDIT : just for information but the bug should be solved : https://forum.winreducer.net/t1634-features-and-services-options-grayed-out#14911