This doesn't happen in Ireland.
You may fail an individual course, and be required to resit the exam in the summer for that course. You need to pass courses of a year to go onto the next year.
If you miss a year, then it is repeated as above.
Therefore in total, there are 4 strikes at a course (year-end exam, resit exam, repeat the year exam, repeat the year resit exam).
If you can't get it in 4 tries, then it is going home time. I have only see this happen once and it was intentional by a student who didn't want to be in medical school (family forced him to go to medical school, he wanted to be an engineer).
....
A different story altogether though is the Irish pathway after graduation for those that chose to try for post-grad training in Ireland. There, there is indeed a scarcity of positions as one climbs the ladder of increasingly higer ranked posts (from intern to SHO, to registrar, to senior/specialist registrar, to consultant). If you finish medicine in Ireland and then do post-grad in US/Canada, then this is not an issue that concerns you.