Hi David, didn't know if it was for you or a client and the 1st post didn't show your company name, so thanks for clarifying.
FYI a listing can be fine for a long time, and then a bot does a recheck and finds a problem that had been there for a long time. So you don't necessarily need to change something for rankings to go south - just so you know for future reference with clients.
OK now others may disagree but I've done consulting for numerous companies where this was a problem and correcting it caused the listing to pop right up.
Look at your description on your G+ L page and how much KW repetition there is. City repeated 3 or 4 times. Main keywords including the KWs in your name repeated several times.
Now have to say that may not be it, because KW repetition like that USED to cause a ranking penalty, but after Pigeon hit it did not seem to any more.
But cleaning it up won't hurt because: 1) Description is not a local ranking factor at all, so keyword stuffing won't help. 2) Google has removed all links to G+ L pages so customers will likely never even see that description either.
So I would totally strip out all keywords especially city and business name. Just do a short benign paragraph with benefits etc. not mentioning all the services.
Try that and see if it helps.