Quick cycling of your flasher is usually caused by extra current in the circuit sa the flasher cycles by heat generated in a bimetallic strip caused by current.

A bad ground can cause some issues, but most often low current.

You could also have a worn out flasher as the bimetallic strip may have metal fatigue.

After exhausting looking for shorts or grounds, I would try a new flasher.

As for the 4 way flasher, I do not think that this flasher is the same as the regular flasher as the current should be higher - it may be in the same can.

My discussion is based on my years of experience with many cars and as trained electronic technician.