The Husqvarna 401 looks to be same motor as my KTM RC390, 373cc single. My 2015 RC390 has over 7000 miles on it and no problems, but...…………..there have been problems with blowing head gaskets and the engine does get hot if ridden in stop and go traffic. I ride mine strictly in the mountains and never in the city. I think KTM updated the head in 2017 to stop any further issues. I will also say most of the head gasket issues I read on the RC forum are on bikes that are raced or track days.
If you were to buy the Husqvarna I would recommend a aftermarket pipe, PCV, and a dyno tune, that's what I did to my RC and it runs so much freer than stock it's unbelievable and I now have 42 RWHP.