Golf 5 2.0 GT 2005, Difficulty Shifting From 3rd to 4th

“I am posting this here for Khetha.”

I drive a Golf 5 2.0 GT 2005 model automatic/triptonic transmission and has a major problem when shifting from 3rd to 4th gear every time. This started after going over a speed hump/bump at a very high speed, engine light appeared on my dash…. now I’ve tried the following:

– reseting the car’s computer system (as someone had suggested the car has some memory loss issues) didn’t work engine light came back soon after the reset.
– changed the transmission fluid (mechanic told me he even cleaned the strainer) put in some new fluid (transmax Z). Oh and the mechanic showed me some metal filings that came out with the old oil.

Nothing has changed and now he is saying it is something mechanical, I need help urgently. Is it even safe to continue driving the car anymore?