faces disappearing and distorting

 From:  Sean (REGULATORJOHNSON)
8300.1 
Hey, quick question. I have been working on the same drawing for quite some time and I recently noticed that some of my parts, which were fine for months, seem to be breaking. Attached is 2 of the parts and while you can see they are still considered solid, the faces in some places are either missing completely or severely distorted. Attempts to repair the parts by trimming off the affected areas cause unpredictable further problems. What is going on here? Since the parts are still considered solid does this even need to be fixed? How can I fix them without completely remaking the part?
Thanks in advance!
-Sean
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