Trio of AEG issues, any advice appreciated please. TM AK, TM M4, CA SCAR-L

[Dentonboy]

Hello, am hoping someone who knows more about faults and repairs could please advise.

1 - broken upper receiver on 00s era TM M4; which brand's upper receivers can be bought to fit and replace please? Plastic is fine! Cheap is fine! Ta.

1 - TM AK47 Spetsnaz firing with BBs hitting the flash-hider on the way out. Assume something is out of alignment. Any idea if this is a quick/cheap fix please?

1 - CA SCAR-L 00s era. Been with ****** ***** for a variety of faults; misfiring; eg gun firing say 30 times but less than 10bbs coming out. HOP rubber changed. Tight ore barrel fitted. Gun came back misfiring and losing air - so low FPS. New HOP chamber and air nozzle fitted. Gun apparently 'not perfect but as good as can be done' by ****** *****. Unsure how it is firing as not collected but assume still maybe misfiring. Any ideas please? New HOP chamber is a CA one that fits but not specific to SCAR as now no longer made.

Hope someone can please advise on these issues. Many thanks.