I've not seen any further information on any maintenance work that apparently delayed departure from Sharm el Sheikh.
The aircraft appears to have ferried from the Moscow DME base to St Petersburg on Thursday morning, and then set off on a somewhat extended "W" from there to Sharm, returning to Samara in southern central Russia by Friday morning, straight back to Sharm, but seemingly on the ground there for 12 hours before departing back to St Petersburg on Saturday morning. There are accounts above of maintenance work at Sharm during this extended layover. What was it ?