as per the subject, I am here asking you to add a checkbox in the Configuration / Interfaces that sends as AT command line terminator for ELM327 1.3 .. 2.1 interfaces not only the \n\r (AKA <LF><CR>) sequence but the \r\n (AKA <CR><LF>).
As i saw from several serial sniffing debug that this is the reason of half of the connection problems with MultiEcuScan with STM32-based clones of the ELM327 PIC chip. In fact, the other half is the well-known 120 ohm CAN bus terminator resistor, but that's another story that requires simple interface HW modification.
I double checked this clue by sending the ELM327 partial command sequence while trying to connect to ECU (not doubling the retries, indeed) from a flexible terminal application and terminating with <CR> or <CR><LF> and I had right replies until first ECU response. I did not proceed with more CAN commands since I did not remember so in deep the OBDII protocol to avoid any ECU trouble.
On the other hand OBDkey 1.4 interface terminates AT with <CR> -making test be successful- but first simple "AT" on live ECU connection is not recognized by ELM327 i tested causing an immediate abort.
If you take into account my request I am sure that many users will have successful connections they haven't so far.
I already scroll through all Feature Request and I saw that "ELM327 v2.1 support" was refused (http://forum.multiecuscan.net/viewtopic.php?f=4&t=4450#p16434) but this could be as simple as welcome by the community.
If you need more information or even coding help don't esitate to contact me in PM.
Best, and have a good job,
SbriXio from Trieste (IT)