Docker container from mongo:3.4 image. Works as expected.
$ docker run -itd --rm --name mongo.test mongo:3.4
$ docker exec -it mongo.test mongo
MongoDB shell version v3.4.14
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.4.14
... warnings ...
> db.test.find({ test:

{ $regex: '(*UCP)test' }

})
> // no error

Docker container from mongo:3.6 image. Throws error.
$ docker run -itd --rm --name mongo.test mongo:3.6
$ docker exec -it mongo.test mongo
MongoDB shell version v3.6.3
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.6.3
... warnings ...
> db.test.find({ test:

{ $regex: '(*UCP)test' }

})
Error: error:

{ "ok" : 0, "errmsg" : "Regular expression is invalid: (*VERB) not recognized or malformed", "code" : 2, "codeName" : "BadValue" }

>

centos7 build of 3.6 from https://repo.mongodb.org/ yields the same error as docker image.