Release 1.4 chap authentication problem on LNS

Chap authentication fails for some reason for the subscriber coming onto vyos LNS. The same user/password pair works on LAC but fails on LNS with the same radius server (freeradius).
Attaching freeradius debug as well as vyos accel-l2tp log outputs.
Same problem appears with authentication mode local and the same user/password - srsuser/srspass
Is that a defect or i’m doing something wrong?

freeradius-debug.txt (8.1 KB)
vyos-accel-l2tp-log.txt (84.7 KB)

i think i understand why authentication failed - LNS calculates chap challenge with empty user name, though it receives “srsuser” within Proxy Authen Name from LAC.
But still no glue how to fix that.
How can we tell accel-pppd to use proxy authentication data received?
This is from iccn:

This is ppp chap message from lns

This is radius access req from lns:

any suggestions?