I am not sure if this is a bug from a more recent version of PyCharm (at least since 2018.3.3 Professional Edition), and I also don't know if it is specific to SQL.
When I type a left parenthesis, the closing right parenthesis always autocompletes. In the past, typing the closing right parenthesis would overwrite or skip over the already-existing right parenthesis. Now, however, typing a right parenthesis in this case only inserts an additional closing right parenthesis so I have to delete the extra. This only started occurring for me in the past few months, and it also happens for a colleague of mine. Further, it happens most, but not all, of the time. (e.g. if I open several parentheses, the closing parentheses do not pile up if I try closing them -- only the last one won't get overwritten)