I'm trying to run a fixed effects panel data analysis with a cumulative file of the European Social Survey from 2002 to 2018 with the command xtset cntry essround.

After having used the encode command for my country variable which seems to work fine, I wanted to include my timevariable as well which the variable essround provides (see picture).
However when I try to run the command I get the following error: repeated time values within panel.

I've read of people who use the following command to combat this: drop if yearvar==yearvar[_n-1] which however leads to me dropping all my observations but 9; the 9 observations which make out each of my time waves of data collection.

How do I solve this problem?

Best regards