I have tried booking with SR and LH search engines to HAV but get "stuck".

I want to FLY LH and AC on the following: DOH-FRA-YYZ-HAV in late April and then fly SR HAV-ZUR-DOH on May 1st or 2nd.

LH says there are issues with connection times, but those connection issues disappear when I start/finish in FRA (and fly via YYZ). Their search engine does not show what the connection issues are, but the flights are the same whether I start on DOH or start in FRA

SR seems to have nothing showing for YYZ and only show YTO so that is the issue there.

Any suggestions?