Echo and crackle problems

First issue - very bad echo since upgrading the distro. I updated from 1.87.something to 1.810.210.57-1 on the weekend. I ran the update scripts consecutively as per the note on the page listing them. Looks like chan_dahdi gets wiped and replaced with a default one… Unfortunately for me, I didn’t expect this, so lost all my changes to it (caller ID detection causes huge delays, echo cancellation settings, etc)

Second issue - I’ve had an annoying crackle since installing FreePBX distro. It’s quite loud, but just sounds like a crappy phone line. I don’t really like it, but in general, the main users of the phone line don’t care too much about this one.
Never noticed the crackle on a test VM I had PIAF on before choosing FreePBX, so I don’t know whether to blame the FreePBX distro or any number of things that could have changed since (not sure if I tested on this line for example, and I think I changed cable used to connect the line so it could be a dud)

I’m after ideas to try right now. If I can’t sort the echo by tomorrow or the next day, I’m planning to revert to a backup image… But obviously I’d prefer not to do that.

Info on what I’m using:
I’m running this as a KVM virtual machine and I’m using a TDM400P clone (in PCIe form) with no hardware canceller.

Look at this thread:

I had similar problems, voice quality is unusable and the chan_dahdi.conf and system.conf files were overwritten. It seems the problem might lie in dahdi 2.6. I have reverted to an earlier version and everything has normalized.

Restored from a backup after reading that… Seemed easier than trying to do anything else.