Hi ManyCraft,
Sounds like the bobbin thread in the top is the clue.
Your needle eye/point size may have been too small for the top thread to move as freely as it needs to move when doing free motion in all those different directions.
You can have good results with a needle and thread when sewing in a straight line, but get a mess of trouble when you want to free motion or do complicated zig-zaggy things.
A the correct needle/bigger needle eye or finer thread can help.