Serialport issue

Hi, I am trying to read data from serial port with no luck. I am using USB/Serial converter with pl2303 and I shorted RX TX pins so I can write data to the serial port from nodered and then read them from Linux console with cat -v < /dev/ttyUSB0, I can also send data from console by echo "aaaa" > /dev/ttyUSB0 and then read them with cat command, but I can NOT read any data in nodered.

I have one Serial Output node which is triggered with Inject node and on push is sending timestamp and I have also one Serial Input node which is connected to the debug node. Both of them have status connected. But there are no data in debug node when I press inject. I can see that timestamp was send by cat /dev/ttyUSB0.

I think that problem has to be in Nodered because serial link is working. Do you have any idea what to do or where are any relevant logs stored which I can use to determine what is going on in nodered?

My setup:
Raspberry pi 3b+
Dietpi - latest
Nodered -latest
Nodered is running with root privileges
USB/Serial converter - Prolific pl2303

Thank you for any suggestions

I assume that you've tried the obvious such as checking that the user running NR is in the wheel group or whatever DietPi uses? Also that you have tried a console based serial terminal to make sure you are using the correct serial settings in the serial-in node?

Also, are there any errors reported in the NR log?

NodeRed is running under the root user so I think there is no need to be in any group. I tested serial link only in unix console by cat and echo commands of /dev/ttyUSB0. I thought, if I set up serial nodes with some settings and then deploy, It will open port with that settings (baud rate etc.) and If i shorted the rx with tx pins of converter it should have correct settings for communication Am I right?
I dont know if there is any NR log /error log, I can read only that log which is in console when I run node-red in console. There are no errors in console log.