custom / extra threadfield don't appear in upgrade xthread, but ok when fresh install

[umetkaran]

some year ago, upgrade mybb 1.6 to 1.8
for xthread, when create new thread. some extra threafield (like Thread Description) not appear in template 1.8, but appear in template 1.6.
of course {$extra_threadfields} there in theme 1.8.

fortunetly, no effect on Global Template. because $tfinput = still work

sometime ago, i try deactive & fresh install xthread = no problem.
but, if i implement fresh install xthread for my non-trial forum. many custom threadfield deleted when uninstall = may, not effective

for time ago, i try theme 1.8 from forum with fresh xthread to forum with upgrade xthread and otherwise.
but, in 'fresh xthread' forum, that theme ok (extra field appear)
and in 'upgrade xthread' forum, extra threadfield still does not appear.

so, i think may be related about 'upgrade XThread' . and may some help for manually way to fix

by the way, my forum still quiet (no advertise). but if someday success enought, ready for donations or coopration
and may be, 1-2 next month. i show my forum in signature

[ZiNgA BuRgA]

This problem exists with many MyBB custom themes and plugins, because MyBB never applies custom template modifications of plugins when a new theme is added.
Reactivating the plugin may fix it.