Here we go again.
How many times has this happened now !
a) It shouldn`t happen in first place.(Especially on new board).(Is screw bottoming out or is it too short ? either could cause screw to strip thread)
b) When it does happen, any sort of filling/adhesive is just not going to be as strong as original which broke in first pace anyway.Adhering to plastic is difficult at best and impossible on occasions.Preventing adhesion to screw itself can also prevent bonding to insert and if not done removing screw will then make problem worse.
c) If you are going to attempt a repair the only structurally sound way is to simply fit an over sized (diameter) screw.(Preferably deep threaded + single threaded) And this will only work if there is sufficient material left in insert to accept an oversized screw.(In UK deep threaded stainless cross head screws are available through IFS, a nut + bolt supplier)
Putting a longer screw in could make matters worse if it bottoms out ! Check depth of insert with a match or something. Make sure screw you use is just getting o this depth after compressing strap etc.
DONT DO THIS NEXT ONE ON YOUR BOARD
Its not impossible to replace entire insert.But its a pain and involves drilling out with an 18.2 mm core drill and re-bonding a new insert. (Available through GUN) Not recommending this route but I have done it on old boards to move footstrap placing or replace completey ruined insert. (I`ve got a 5 year old F2 Style which gas had an insert of this type in since a year old and has been heavily used with no signs of insert moving or stripping.!) (But I did not use suppied screw with inserts.Best screws available are off older F2 boards !!!, really deap threads to cut deeper into plastic.)