Lebanon humidity will beat a sealed bag that was opened last month. Wet PETG strings. Nylon pops and goes foamy. TPU refuses the first layer. The slicer is usually innocent.
What we do in the shop
Engineering spools sit in dry boxes. Before a nylon or PETG job we dry if the bag has been open. PLA is more forgiving but still ugly if it sat on a damp shelf.
If you print at home
A filament dryer or a food dehydrator beats a kitchen oven you cannot control. Typical: PETG 55–65°C a few hours; nylon hotter and longer. Do not melt the spool.