The full Russian Orthodox Priest's Service Book (Sluzhebnik) contains exhaustive instructual material in an Appendix called "Uchitel'noye
Izvestiye" -- ("Instructional Information" may be the best translation).
It contains detailed instructions to the priest how to prepare for the Liturgy and what to do in a very wide range of circumstances if something should happen during Liturgy with the priest or the Holy Gifts.
Regarding the subject under discussion, in this Appendix we read:
"If after the consecration of the bread or the wine a miracle should
appear, namely, that the appearance of the bread would become that of
flesh, or of a child, or the wine appearing as blood, and if this
appearance does not change shortly, meaning, if the appearance of bread or
wine does not return, but remains unchanged, in no way should the priest
commune, for these are not the Body and Blood of Christ, but simply a
miracle from God, manifested as a reult of disbelief or other cause,--let
the priest take another prosphoron (if only the appearance of the bread
changed), and as shown above, let him perform the proskomedia actions and
words with it, let him take out the Holy Lamb, and having set aside the one
that has been miraculously changed and preserved it with care, let him
begin with the prayer "With these blessed powers we also...", and let him
perform all in order, but repeat nothing over the chalice. If it is in the
chalice that the appearance of wine has changed, let him into a new holy
chalice, or having poured out the contents into another vessel, into the
chalice pour wine again, saying the words of the proskomedia over it, and
so, let him consecrate it as usual, and at the time of Communion let him
commune as always, and complete the service.
"If shortly that which had appeared as flesh, or a child, should again
appear to be bread, or in the chalice, that which had appeared to be blood
should once again appear as wine, let him not sacrifice another lamb, or
pour new wine into the chalice, but let him commune with these, and so
complete the service: for they are the true Body and Blood of Christ."