This issue happened to me for the first time today. Very annoying having to wait so long to boost buildings again.
(And not sure if related, but it was right after I closed the video ad accidentally before it was finished, I never do that and it was the only uncommon thing I did before the cooldown was there.)
Why don’t you do something to stop all the inconveniences caused by this issue while you are working on a possible fix?
We had events that could temporarily solve this issue with 100% efficiency before,
"Community Week" had the perfect benefit for this situation:
All Production Boosts activated for everybody
I thought you would notice it and just add that to upcoming events while the issue is not solved yet,
but I don’t see it on the benefits list of the Blacksmith event so I’m leaving my suggestion here.