Issues with serial port - additional characters

I have just soldered on some leads to an Arcadyan AW1000 router to gain root access. However it's not working as intended - when I type into the terminal it acts strangely, adding characters as I type.

Screenshot 2023-05-31 082247

What could be the issue here?

Although I cannot answer your specific question about the serial port issues...

This device doesn't appear to be supported by OpenWrt.

This would mean that there are probably very few people here who will have used this device. It does appear that some work was done to try to get official OpenWrt running on the unit, but it seems that it stalled out.

Therefore, it may make sense to try other forums where the device is supported if you wish to gain access this way. Otherwise, even if you get the serial port working properly, you probably won't be able to do anything interesting since official OpenWrt isn't supported, anyway.

Several ipq807x devices require an 1.8V based UART connection, did you measure the voltage beforehand (does your USB2serial adapter support it)?

That was actually me that posted that thread...I didn't have any issues with UART then!
I'm taking another stab at our home network and went to connect to serial and I'm met with this garbled input .

@slh - I've tried 1.8v and although receiving works fine it appears I can't transmit. IIRC I accessed it with 3.3v when I first started playing with the device.