We have experienced the problem with the loose handle on our Kenmore range oven door for the last four years. Tightening it several times a week. Poor engineering seems to be the problem, Metal screws heated by the oven inserted into a plastic screw hole. The forums I visited suggest the problem hasn't been corrected on replacement handles.
I encountered what seems to be a no cost solution while browsing through an old, old edition of Popular Mechanics Magazine. The writer suggested when dealing with screws that were stripped out to take some braided copper wire from like a 16 gauge extension cord. Strip off the insulation , unbraid the wire, and insert it into the screw hole, then tighten the screw.
I tried this several months ago and to my amazement I have not had to tightened the handle on the oven again in that time.
Seems to be working for me!