According to the Guardian here:
Ukrainian officials said Gazprom had "deliberately" sent the gas by a route that would have meant switching off gas to Ukrainian consumers in the east of the country. Instead of supplying gas via the traditional route, through Ukraine's Belgorod and Rostov region, it had been sent on a bypass route which would paralyse supplies to the towns of Donetsk and Luhansk. "This is just provocation against Ukraine," said Bohdan Sokolovsky, Ukraine's commissioner for energy security.
Now why would Russia care about Donetsk and Luhansk? Because they belong to the part of Russia that usually supports Russia. This forces the European-leaning Ukrainian government to choose between supplying Europe and cutting off the east of Ukraine, or keeping the east happy and cutting off Europe. Fighting the coming election by gas flows? Looks like more mischief to me.
There's another lot of nasty stuff from the Ukrainians about Nazi tactics over the siege of Leningrad, none of which is going to help deal with the commercial issues of the gas price, which needs to be settled before things can get back to normal.