After Russia "liberated" the country[1] citizens living abroad were ordered back to the motherland. For him this was a really tough decision, since people who refused were criminalized and he would have faced jail if he returned to the country.
He told me that whenever he went from Zurich to Vienna he took the train, which takes 9 - 12 hours compared to the flight, which takes roughly an hour.
His reasoning was that if the plane, for whatever reason, is diverted to Bratislava he would be truely and royally fucked.
At the time he told me the story I thought he was a bit paranoid. Looking at what happened in Belarus I'm no more so sure. And he was just a potential convict not a prominent disident.
Thankfully he could return after the velvet revolution[2] and he now lives in Prague.
[1] https://en.wikipedia.org/wiki/Warsaw_Pact_invasion_of_Czecho...