For the following equivalent questions, you choose
whether-or-not the 3 variables in a clause must be distinct.
Is there an integer $k$ such that for all 3-SAT formulas $\mathcal{F}$ without negations,
if every $(\leq k)$-clause sub-formula of $\mathcal{F}$ is 1-in-3 satisfiable then $\mathcal{F}$ is NAE-satisfiable?
Equivalently, is there an integer $k$ such that for all
3-SAT formulas $\mathcal{F}$ without negations, if $\mathcal{F}$ is not NAE-satisfiable then
$\mathcal{F}$ has a $(\leq k)$-clause sub-formula which is not 1-in-3 satisfiable?
(The Fano plane shows that $k$ can't be less than $7$.)
Motivation: That is the "low end" of my question
on cs.stackexchange which was inspired by the
possibility of generalizing Schaefer's dichotomy theorem
to constraint satisfaction promise problems.
Specifically, for the simplest non-trivial promise-constraint,
with m being the size of the input set, I have neither managed to
find evidence for it being in promisecoQIP[2]TIME$\hspace{-0.02 in}\big(\hspace{-0.04 in}$2o(m)$\hspace{-0.03 in}\big)\hspace{-0.04 in}\big/\hspace{-0.04 in}$q2o(m)
for infinitely many m, nor find evidence that it's not solvable
in coNTIME(O(1)) on essentially the most basic word RAM.
The former applies even when each variable occurs exactly twice
and "many m" gets replaced with "many even m" (since 3 is odd),
and the latter applies even when negative literals are allowed.