Perhaps if the Soviets decide that they shan't roll the tanks in if things look a bit shakey in other Communist countries. This might, in the short term, result in some socialist regimes being overthrown, but I don't really think it will result in any kind of reverse domino effect like we saw in the 80s and 90s - the intelligentsia is still solidly socialist at this time, and communism won't be seen simply as an instrument of Russian imperialism.
Meanwhile, the Soviet Union turns its attention south, perhaps involving itself in a terrible war in Iran. The propaganda about the Warsaw Pact being a free association becomes much more believable as the Soviets can't really militarily hold Eastern Europe. Starting in the Balkans, communist states start to form their own bloc seperate from Moscow.
The Iran War ruins the USSR, and by the late 70s, market liberalisation and courting the West becomes the only avenue left for the Kremlin to follow in order to balance the books. The Warsaw Pact, not feeling anywhere near as much disatisfaction with socialism as OTL, remains socialist.
This liberalisation strikes the Baltic Republics, and in the early 80s, they are granted independence, provided they remain confederated with each other. Around the same time, the WP renames itself the European Peoples' Community, to mirror the European Economic Community on the other side of the curtain.