[R-meta] Conceptual Question: test of moderators CHE RVE vs 3LMA

[Noah Schroeder]

Hi Everyone,
 I am learning about CHE RVE meta-analysis and have been experimenting
with it. Something I have noticed is that occasionally, my test of
moderators pvalue will be NA. However, if I run the same code through
a typical three level structure without CHE RVE, I get a pvalue for
the test of moderators. I have the following conceptual questions I am
hoping someone may be able to help with:
1) what might cause this NA pvalue to occur in the test of moderators
when using CHE RVE?
2) Should this NA be interpreted? If so, should it be interpreted as a
non-significant result on the test of moderators? I noticed that when
this occurs i generally have notable overlap in the CIs.
3) In cases where i do get a pval for test of moderator, the levels of
the moderator with only 1 comparison do not provide tval, pval, or CI.
Is this because there is only one comparison at that level, so it is
unable to make estimates to other comparisons within that level?

For context:
3LMA code: structured similar to this code from Harrer et al.'s book:

full.model <- rma.mv(yi = z,
                     V = var.z,
                     slab = author,
                     data = Chernobyl,
                     random = ~ 1 | author/es.id,
                     test = "t",
                     method = "REML")


Conceptual overview of CHE RVE code:
set rho
set V with impute... from clubsandwich
Similar structure for 3LMA, swapping V for the set V value.
then using robust(model,... clubSandwich = TRUE).

[sorry for not providing actual code, i don't have it on this
computer. i can provide it if it is essential to answering the
question].

I am a self-taught R user, so if I am missing something really
obvious, please don't hesitate to point it out. Many, many thanks - i
have learned a lot from reading the old messages in this mailing list
(apologies if this has been addressed before and I missed it) and the
various example documentation online, and thank you all who have
developed resources for R!

Best regards,
Noah