Panasonic KX-NT546/543

I never had any problems with V2.01, are you sure the file is not corrupted?
What model of Panasonic PBX do you have and what version?
The PBX must also be a compatible version.

I had a problem with 543 and 546. Subscribers were not heard at times. The firmware was 2.002. I installed 2.001 and everything started working fine. But there are two 546 phones on firmware 1.010. When loading the firmware from NS500 008.03023, the phone simply reboots. The rest were flashed successfully.

I assume that you need to install a transition firmware, for example 1.011 and then install 2.001. On these problematic phones there is a bug when downloading files from the network on the computer (the computer is connected via the phone). When the user downloads a large volume, the phone reboots.

Won! Raised an FTP server on the computer and through the TDE100 console utility (transfer via ftp). Also connected the phone via a power supply, not via PoE. Disabled VLAN. Everything was successfully flashed to version 2.001