yes, it's a PITA... I get to fix a couple each month just like yours. The original vent in all 020T and MS200t up until about a year ago had a sponge-like material in the tank vent hole. They got crushed and damaged and then leaked. Stihl brought out a "vent kit" which had the vent on a the end of a inch section of fuel hose, but it spit the hose after a lot of stress. They changed it again by bringing out a lighter weight vent top, but the problem came back. It only takes a few minutes and a few cents in fuel hose to change it, but..
To convert to the new system where the vent is secured in the handle means you have to change the handle housing - not for the timid... and expensive. Tie wrap or a blob of RTV works well...