Troubleshooting MGC68

Hello gentlemen (& ladies if there's any on the forum) ,
I seem to encounter many MGC68s that have a loose upper receiver when it's snapped into place with the lower receiver/gripframe The upper receiver seems to have so much play and can be twisted slightly & rotates when it place. Is there a DIY remedy for this or do I need to send my MGC68 to an expert for a bit of welding
Plus the fold-out stock, when extended, doesn't stay in place and tends to sag an inch or so from its intended position Could this be tightened to keep it in place ?
I would also love to by an original barrel nut spanner for tightening or removing the barrel if anyone happens to have a spare one for sale
Please let me know, thanks in advance.
Broomie

hi

weld / braze a washer under the take down hole, where the plunger is

Hi,
First I got to find a washer that will fit tightly on the plunger but it needs to be pretty thin cos It has to be shaped to fit the underside of the upper receiver which is a curved surface. Then I need to find a welder who won't get freaked out as I am in a very P.C part of the country Yikes ... I guess it's not a DIY job
Thanks,
Broomie
P.S. I also notice , depending on the model, the sear of the trigger group varies a lot in width Wonder if this also allows a lot of lateral play / looseness in the upper receiver when it's mated to the lower gripframe