How does your clogged freon line get clogged if you do not have a leak in the system?

If no work has been done to the unit it will not clog up by itself unless it has had a very bad burnout that plugged up the strainer screen with the varnish and debris off the windings and then it would not be running anyway.

Thanks, no work had been done except an ac repairman had added a booster to start the compressor. We added the booster because the repairman said we should get another 5 years out of the system. The system worked for 4 months after that and then quit.