Ref. No. 40/1078
In the name of Allah the most Gracious the most Merciful
The answer to your question is as it follows:
The Musafir Muqtadi is also obliged to follow his Muqeem imam in all arkan (obligatory acts) of salah. If musafir muqtadi didn’t follow his imam in 3rd and 4th rakat, his namaz will not be valid.
And Allah knows best
Darul Uloom Waqf Deoband