questions..questions...
yes, Guy these questions pop up to mind but other factors should be also under consideration:
1. how busy was the sector?
2. R/T freq. congestion (or condition)
3. russian pilot's english level
...these are (inter alia) some questions that pop up in mind....
Answers should be very carefully joined together so that correct conclusions are drawn and put to prastice ASAP to avoid similar situations in future (here I speak as a front line radar ATCO)...