Next would be opening the chassis and carrying out an
inspection of the wiring to the ESC and motor to see if
there is a break there. A broken wire or intermittent
connection can lead to false or incomplete signals to the
ESC or motor giving erratic control and flight. Have a look
at the esc for signs of burning or bubbling of the
components which may indicate overheating.
If the wiring and ESC looks good then the problem
probably lies within the esc or even motor. There is no
really simple home test for these parts other than to swap
them with a known good one to see if this solves the
issue. However if you feel able to then there are further
tests to see what has failed.
Third test