No clue what happened to my reply, it just vanished....
Ok, let's try it again....

Use Notepad++ - free and a great editor with good search and replace functions.
Made a small and simple cube and slice it.
Open the gcode file with Notpad++ and scroll through to find the Z moves or if commented just just look for the comment for the layer change.
Flashprint should create code with comments like this:
;layer:0.27
The ; means it is a comment and you can search for ;layer and skip through to check the values.
If you sliced with 20 odd layers and only find a few layer changes in the code you have a problem with Flashprint or your STL files are somehow bad.
The layer comment should always go up the same amount as your set layer height.
If it does not, check if you accidentally activated the variable layer height feature for some part and it still sits there instead of using a lixed layer height.
Same for the new feature of cutting your print job into different parts, sometimes flashprint forgets the setting should be refreshed and a new part is not sliced fully - you would see that in the preview window as parts being too short in height or just having a slice of the whole.

If you do have all the layer change commands present then try to print a simple cube with little infill at a layer height of 0.27mm.
Might be a bit of a hassle but try too keep a finger on the z axis threaded rod.
If the layers won't change but you feel a "bump" in the rod every time the layer should change it could be that your motor current is too low.
Or, if all manual movements work fine that you try to move your z-axis way too fast - try a value around 15mm/s if you have anything above 20 sitting there.