1299 is a cylinder head temperature sensor. Diagnose proper and/or replace. Check your coolant level as well

No. Get a new one is pretty much the only option that fixes the issue. Gluing and epoxy could work in rare cases…but to even do that correctly, you should remove the radiator and do it on a bench and that is a crapshoot as the radiator tank do get pretty crispy due to age, heat expansion and cold contraction over time. These radiators are pretty cheap so why would you invest in removing it without replacing it.