Sorry, I don't know the G-Lab controller…but think I know what this is happening.
I had exactly the same problem with a Rocktron MIDIMATE and it is to do with the way the switches work on the controller. the easiest solution is to change the way the switch on the controller works, change it from a "Latching" style to a "Momentary" style and it should fix it…..the problem was you can not do this on the MIDIMATE, but you can on the other controllers I have tried (Ground Control Pro and Fractal MFC-101)
the reason it is happening is that the switch is set to "Latching" and this is like a stompbox. press once for "On" and press again for "Off"
the MIDI CC for "ON" is usually CC Value "127" and MIDI value for off is usually "0", so when you tap out a tempo on the switch the MIDI data sent is 127,0,127,0 etc. the Factor pedals only listen to values above 64 or 67 (can't remember the exact figure) so they would only process the 127 value and totally ignore the "0" for every other switch press which gives you 50% of the tempo you were expecting.
Assigning the switch to be momentary will fix this as each press will send the on CC value of "127" if you can not set the switch type to momentary see if you can assign the vallues for on/off to something other than "0" and "127" to something like "90" and "127" as this would then trigger the correct tap temp you would expect.
Hope that helps