another way might be to pop rivet it..I know I could fix it if I was there...bring it by my house and I'll fix it... I've done so much with so little for so long, I now can do anything with nothing....lol....the other way could be to run longer screws that grab the other side of the tube... or through bolt it with nuts on the other side... looks like it's an on going problem that need to be re engineered ...first figure out why it's coming loose... then the fix will be permanent ....is the attaching part aluminum? you could cut out the section and weld thicker metal that you could thread...
but I have a welding fab shop...and like I said... just bring it by and I'll fix it to where you never have the problem again...