I inserted a system break and a tie becomes a tiny dot on the screen, yet I believe there is room to draw a proper tie. If I delete the system breaks the tie is ok as per image attached.
The reason for the problem is in the red box at the end of the system. 105.7% means the system is overfull, and Dorico is trying to squeeze things together more than is optimal. You might be able to move things around somewhat using the Note Spacing Tool in Engrave mode, but there should really be a System Break one or two barlines before the end of the system. You might even be able to stretch that particular tie in Engrave mode, but things really are squashed up more than they should be - look at the dots on the half notes in the third and fifth bars, for example.