Quickbuilds have been often plagued with mold
The hall I used to go to had that happen. Hail damaged the $60,000 concrete roofing that was sold as never needing replaced or repaired and the JW roofers who replaced it roofed right over all the HVAC and sewer vents. Then COVID hit and for three years that hall sat empty with sewer gas, and HVAC condensate filling up the interior. Coupled with landscaping that ran run-off water towards the building they have had to remove all the brick work, replace all the wall sheathing, and many of the wall studs. Then they keep "reminding" the ones still going to "show your love for Jehovah and remember to donate for the high cost of this repair."
They should have just demolished the building and sent the remaining members to the hall in the next town ten miles (US) over.