Currently ThinLinc is pretty much unusable in full screen mode when there is different DPI scaling going on for different screens. The monitors on server side are heavily out of sync with the client's actual monitors.
What seems to happen is that Windows reports the scaled dimensions for each and every monitor. However this results in two issues:
a) The monitors do not line up as the scaled width of one monitor might not match the differently scaled offset of another monitor
b) The client is just a single window, so it will be scaled according to just one of the monitors, meaning the dimensions of the other monitors are incorrect if they used a different scaling factor.
The issue is also visible in the new monitor arrangement selector in the client settings. See this issue upstream: