This has popped up in the past, nobody has found the cause or a fix. It somehow appears to show it's ugly head when bridging calls!
It's hard to diagnose because it doesn't happen all the time if at all for most users. It may be that voice frequencies are triggering DTMF. Talk-Off, or Talkoff, is the term that describes when a human voice is able to trigger touch tones, or DTMF tones during a telephone call. Talk-Off occurs when a signal processing system tries to translate sounds into to touch tones. Some people's voices are able to recreate touch tones frequently relative to the general population.
A similar issue was posted here: Obi202 with Obiline as an extension to FreePBX - DTMF on incoming call
Unsure if this is firmware related or a a glitch in the OBiLINE itself, personally I haven't ever encountered the issue. Can you provide any further information such as could the other person hear the tone or was it only heard by you? Has it happened since? Were you on speaker phone (either end) or using the phones handset?
In the meantime, let's try making the following change on your OBi202 and the first OBi1062 device you purchased. Log in to each device and navigate to Service Providers > ITSP Profile D > General
and configure the DTMFMethod parameter like so:
Do the same for ITSP Profile C > General
on your OBi202 and the second OBi1062 you purchased recently.
Now we wait! :)