Option Set Id cannot be changed Error
We got this error while importing the solution. This issue is caused by having an optionset with same name but different guid.
The solution is to identify the field and delete it from the org where we are importing.
select name from optionsetview where optionsetid = ‘c0864f8b-2c13-e411-93ed-000d3a800961’ (the 2nd guid)
The helpful post