@Nick78 have you been tested for MODY? (I know nothing about it other than it is not T1/T2 and is genetic). I can totally believe that a LADA person would find gliclazide ineffective long term though, as it depends on stimulating the insulin production by your pancreas. As for reactions to insulin, the different varieties have different preservatives, so you may just have been unlucky with tresiba. (Disclaimer, I am not a doctor, that is just a wild guess).
Don't give up, even long term T1s (52 years for me) find that their insulin needs vary. There is a long standing joke on the T1 forums that the colour of your socks varies your insulin needs.