I thought of getting a set of 4 ESCs of different brand later so temporarily I've used my old Plush ESC which seems to be working fine. I didn't have a complete flight with it yet. I saw the same brand esc on clearance sale in this forum, let me check with him.

Can you assure that its the 45A esc on a 12A motor is the only reason for a crash. lot can go wrong leading to crash.
R&D? Its safer to use a higher rating than the motor rated for than getting close to it since there will be a spike in input current during start and the current will reduce gradually as the motor speeds up on no load. and might get lot of issues like ESC trips with a lower ESC.
nevertheless, its not adviced to use different rated esc on multicopters.

Ashok.P

sir everything else was used in the next plane my friend bought, only the motor and ESC were removed ,we bought the same plane(we just replaced the electronics,we took out the 700mah lipo and placed a different lipo ,he even balanced it and after the crash it was only the motor that was damaged) and im advising him to use a 20 amp esc not a 15amp (it should be enough) but as he has invested in 4 30amp ones he can use them but with caution...ultimately its his choice
p.s-R&D(research and development)

Today I had a successful flight with this setup. It was about 10min duration. There was no sync issues, motor overheating or any others. It might be due to reduced ESC refresh rate which I have set manually (although not sure exactly). I just wanted you guys to know about this. Although I'm planning for a replacement ESC of the same brand & rating which I couldn't find. Maybe I just have to wait until any LHS stocks this item or get it from abroad.

Good.do you want the dys 30amp? If yes pm me...

MPU in ESC, find the number on it, and chk the schematic diagram, one must be qualified understanding circuitry in electronic s, in it you will find one of the pin having OVP,Over voltage protection or voltage sense or voltage limiter, here this pin sense voltage of Output or Input,  and if it detects its fixed ratings then you will here beep if provided for trouble shooting,  else good technical guy can solve, well Ican solve your problem but I need a spares for replacement,  you mayhave FET bad or intermediate or leaqs, I can test that with my multimeter, or chk capacitors , chk PCB tracks for tiny cracks , cuts, PCB printed Circuits board,