TCL IVR dtmf events (ev_digit_end) not received when legs connected

[A C]

Hello,

on c8000be Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 17.6.6a tcl script does not receive ev_digit_end events when two legs are connected.
Events are correctly received when legs are not interconnected.

Similar script works 100% on older versions/platforms (ISR 16.12.2s) 

Any hint?
Is there a bug around?
Thank you

[A C]

Upon further investigation, it works on a POC script, so I definitely think there's some oddities between version, but when properly programmed, the features appears to work on said version.
Thank you!