Pressure Balance Unit in Shower

I have a single lever handle shower, just had a new pressure balance unit installed. The lever wasn't put back correctly, and when the shower is turned off, it goes way past the "Off", and when turned to "Cold", it is now warm and when turned to "Hot" it is scalding. However, the problem is the shower will be cool, then a blast of hot will mix in for a second, and this will go on like this the entire time. Does this have anything to do with the lever being put back incorrectly, or can it be a faulty pressure balance unit. The mixing of hot and cold are just not working at all. Please advise
Thanks,
jdserb

Call back the contractor that supplied and installed it to correct the problem.

delta

The "rotation/temperature" limiting stop was not replaced when the handle was installed. Without it, the operation is erratic.