A puzzle about adverbials in simultaneous readings of present and past-under-past in Russian

The present and past tense can both get the simultaneous interpretation in comple-
ment clauses when they are embedded under the past tense in Russian. However,
I observe that the adverbials that are allowed with present tense in such contexts
(for example, sejčas ‘now’) are not allowed with the past tense and vice verse (for
example, togda ‘then’ is not allowed with the present). I show that simply restrict-
ing the meaning of those adverbials does not help due to the fact that tenses can
be interpreted de re. In de re construals, tenses are interpreted outside of the clause
they originate in, so no meaning conflict between the tense and the adverbial in
the embedded clause is predicted. I propose that when a tense is interpreted de re,
an adverbial has to be interpreted de re together with it. I show that under this
assumption the observed restriction follows in a direct way.