That seems like something for TAC. Here is what I found:
Error Message SUPERVISOR-3-FATAL: [chars].
Note This message applies only to Catalyst 3750, 3560, 2975, 2970, and 2960 switches.
Explanation An internal error occurred in the supervisor ASIC. [chars] is the detailed error message.
Recommended Action Copy the message exactly as it appears on the console or in the system log. Research and attempt to resolve the error by using the Output Interpreter. Use the Bug Toolkit to look for similar reported problems. If you still require assistance, open a case with the TAC, or contact your Cisco technical support representative, and provide the representative with the gathered information. For more information about these online tools and about contacting Cisco, see the "Error Message Traceback Reports" section.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...