AT commands always replied with ERROR

Hello all,

i have one case of a SL8082T modem that stopped working in my application. In this case my system cannot really communicate with the modem.

In order to have at least something i had to set the MCU baudrate to 9600, send three times AT\r (i read that this causes the resynchronization of the uart) and only then I could make the modem echo my commands, but all of them (till now i´ve found some exceptions) are replied with ERROR. Starting any command that doesn´t start with ‘a’ or ‘A’ results in no echo from the modem.
After 5 min without sending commands i received a message from the modem: *** TIME OUT ***



Any ideas on what could cause this? Until now i couldn’t set a different baud rate, tomorrow i’ll try more.

Thanks for the help!
best regards