Hi Soon,
For this phase,we could only opt option Accept non severe error only.For more details you could check with SAP KBA 2050604 - Problem analysis in upgrade: Phase ACT_UPG
It ' s too risky to ignore 400++ objects.
Yes it would be risky if we ignore system severe error during the phase and will produce issue in further steps as well.
So here i suggest you to only Accept non severe errors for the system and continue the phase.
Regards,
Gaurav