Critical Issue
When you configure the HDMI TX core at 2 symbols per clock, your design may fail setup timing in every one out of ten Fitter seeds, with less than 100-ps negative slack. This issue specifically affects designs using Arria 10 GX and Stratix V GX devices.The critical path resides within the Transition Minimized Differential Signaling (TMDS) encoder.
To work around this issue, turn on the Aggressive Performance Optimization mode in the Quartus Compiler Settings to achieve timing closure.
This issue is fixed in version 15.1 Update 1 of the HDMI IP core.