I think you can fix this quite easily yourself for now by editing the runtime.js of the platform behavior a little.
Find the part where it says the following:
cnds.IsOnFloor = function ()
{
// Must be overlapping solid in current position
if (!this.runtime.testOverlapSolid(this.inst))
return false;
and change it to:
cnds.IsOnFloor = function ()
{
// Must be overlapping solid in current position
if (!this.runtime.testOverlapSolid(this.inst) <font color=green>&& !this.runtime.testOverlapJumpThru(this.inst)</font>)
return false;
The added part is green.
Tried it in my project and it seems to work fine. I'm not an expert though, so use at your own risk and save a copy of the original runtime.js if you want to try it.