I would need a c3p file or a screenshot to help and know I'm pointing you in the right direction. However, I'm going to assume that you are using the on touch hold, if so replace that with this.
Event: Is in touch; Action: Wait 0.15
Sub event: Is in touch; Action: Heavy Gravity
Else: Gravity is default
This may not work 100% of the time or as intended so test it well and play around with it.
Sometimes you got to work around the engine, but that goes for every engine.