I hope you did fully reflash using QFIL package first.
Then you did factory reset via telnet.
If so .... last idea is to de-brand that device, and try update it after with Jolla C firmware.
So, with putty (or any other client), make telnet session,
and choose option 3 (SHELL), then carefully read
THIS and do required steps
After done, exit shell and select option 1 from menu.
p.s.2 that procedure above will update "auto-restore/factory reset" partition to this version :
JollaC-2.0.2.43-l500d-in-0.0.1.24 , so after making factory reset, that will be version of device,
and at the same time it should be debranded from intex.
test and post results.
b.r.
Alex