Internal Error: Sub-system: U2B2_ROUTING, File: /quartus/db/u2b2_routing/u2b2_nd_routing.cpp, Line: 1681 - Internal Error: Sub-system: U2B2_ROUTING, File: /quartus/db/u2b2_routing/u2b2_nd_routing.cpp, Line: 1681 Description Due to a problem in the Intel® Quartus® Prime Pro Edition Software version 18.1 and earlier, you may see this internal error when running the Fitter Retimer stage or the Fast Forward Timing Closure Recommendations. This error occurs when the preservation level of a design partition is changed to final before running the Fitter Retimer stage or the Fast Forward Timing Closure Recommendations. Beginning with version 18.1 of the Intel® Quartus® Prime Pro Edition Software, this may occur when one of the following Quartus Settings File assignments is set to ON. FLOW_ENABLE_HYPER_RETIMER_FAST_FORWARD FLOW_ENABLE_EARLY_PLACE ENABLE_FORMAL_VERIFICATION ENABLE_INTERMEDIATE_SNAPSHOTS Resolution To work around this problem, rerun the Fitter Retimer stage or the Fast Forward Timing Closure Recommendations and it will pass the second time. Custom Fields values: ['novalue'] Troubleshooting FB: 588360; False ['novalue'] ['FPGA Dev Tools Quartus® Prime Software Pro'] novalue 18.0.1 ['Stratix® 10 FPGAs and SoCs'] ['novalue'] ['novalue'] ['novalue']