Slow file transfer speed between phone and NAS

[Phil_Libra]

Phone : Oneplus 9 Pro
Router : GT-AX6000 and RT-AX86U
NAS : Synology 916+ with USB 2.5Gbps
Transfer speed : FTP - 20-30MB/s ; SMB2 - 10MB/s

I testd a laptop with AX200, transfer speed can be 100MB/s.

I also testd the phone with LibreSpeed on NAS, everything's OK:

And I tested the phone with Xiaomi Mi AX6000 before, the transfer speed is more than 100MB/s.

Can anybody help me?

 

[Phil_Libra]

When I changed the FTP mode from Active to Passive, the speed is back to 100MB/s again...