Not the sort of discovery you want to make!
It has lasted since 12th June 2019, when I poured the resin in the canal in the morning, and discovered the original 3 cracks the same day.
Not sure why this has happened now.
We have had colder nights than last night.
I will leave it for now and see if it moves before attempting to repair.
I know I still have some resin leftover, not sure about the catalyst and the murky water tint though.