Voting and post-voting shenanigans in Croatia aren't unheard of, although most people believe that it happens mostly on local levels and not in a way that alters grand scheme of things. For example, last year ruling party HDZ lost both elections for European Parliament and presidential elections despite result being tight.
This year, however, COVID-19 might change things. State Electoral Commission issued instructions banning anyone being tested positive or merely suspected of having COVID-19 at the polling stations, while not issuing instructions for those persons having their votes collected at homes (as it is usually the practice with disabled or seriouly ill votes). At the same time, government lifted all restrictions for cross-border traffic with Bosnia-Herzegovina which would allow tens of thousands of voters living in Bosnia - and who almost exclusively support HDZ - to participate at elections.
The HDZ getting votes from voters living abroad sounds extremely similar to how the Hungarian party Fidesz gets votes from people in Romania and Ukraine...