Rechargeable fan considerably slowed down even on DC

Felt site is going too slow so though to drop a post here as I am trying to revive my old rechargeable fan. First of all a foolish mistake I made 3-4 years ago was that I purchased OSAKA rechargeable fan even knowing that SOGO is the best in market. It worked ok for a season and then problems started. Its quality was so bad that even its plastic parts started breaking and main issue was that its speed became dead slow.
I thought that its due to battery issue but it even runs slow on AC. I suspect either its transformer is worn out and needs replacement or its motor is of low quality and is worn out so I should replace it.

Need best idea of what could be wrong and what should be done to revive it…
Here is the image of the culprit …


Could be a semi jammed motor. Try to turn the blades by hand, and you can judge if it is jammed or not.

motor doesn’t seem jammed… I opened everything apart and motor too… it moves fine when rotated with hand. That is why I am bit confused what could be causing the issue.
2nd culprit could be the transformer. how to test that?

If motor is not jammed/clogged/etc, it is likely it is either not getting the required power or else, the motor core has or is loosing its magnetic properties. Either issue requires a technical person to measure and inspect. You might need to take it to any electronics repair market to have it checked.

I suspect these issues also… I wanted to do a DIY and not consult to market people as mostly they are interested in getting money by any means.
I have uni-t meter so I can do basic testing if you guys can provide directions about what and how to test