Yes, this backlog seems to being caused by infrastructure and training falling short of where it should be (or solar going faster than expected). It should have been predicted and plans set in place years ago so this would all be seamless.

The concern now is that production will be throttled back and the companies doing the installations will suffer.

Here in the UK they cut the feed-in-tariff (the amount you get paid for putting spare electricity back into the grid) and that wrecked the industry overnight.