Bot authentication fails due to "Signing Key could not be retrieved at JwtTokenExtractor" error

Does anyone have any suggestions on how to resolve the below issue? 

TLDR

It seems like Microsoft Teams is sending my bot a key ID (ZyGh1GbBL8xd1kOxRYchc1VPSQQ) that is missing from Microsoft's list of well-known Open ID keys (https://login.botframework.com/v1/.well-known/keys). This means my bot is unable to authenticate messages that Microsoft Teams sends it.

Details

Today a couple of our development and staging apps started getting this error:

JwtTokenExtractor.getIdentity:err! AuthenticationError: Signing Key could not be retrieved
at JwtTokenExtractor.<anonymous> (/home/gabrielx/projects/oss/oss_ms_teams/node_modules/botframework-connector/lib/auth/jwtTokenExtractor.js:174:15)
at Generator.next (<anonymous>)
at fulfilled (/home/gabrielx/projects/oss/oss_ms_teams/node_modules/botframework-connector/src/auth/jwtTokenExtractor.ts:11:1)
at processTicksAndRejections (internal/process/task_queues.js:97:5) {
statusCode: 401
}

This is an expired, decoded JWT from the authorization header from a bot message that Teams sent to my development environment:

{
header: {
alg: 'RS256',
kid: 'ZyGh1GbBL8xd1kOxRYchc1VPSQQ',
typ: 'JWT',
x5t: 'ZyGh1GbBL8xd1kOxRYchc1VPSQQ'
},
payload: {
serviceurl: 'https://smba.trafficmanager.net/amer/',
nbf: 1628117449,
exp: 1628121049,
iss: 'https://api.botframework.com',
aud: '43f91f57-0c80-40a1-bdbb-79c2f2100ef3'
},
signature: 'yEg_trg3mNyA2noHZd20BAjjonR_YxU9hpTodceVQU1yYJmQR89mhJFNiA0QUZJXE95rsw-mGBVHkCQ5A6NUUgxYOs1Dr-9liSox8lm3xSykOIwnU6xLhoF54U6usRjq82es3hEvZbBZ160HVr3LAMagtBcfdS-SSY2SWDWL_FUpAGq835r-IIrSDzV8T5GVIWDFzNSPdqYGT_7iA2QOQDBnouh53V57TGPIBzvylmRyquLe3f_b4MBi4TdpLPXvmlQQejaW10WY2BolHewYVltrIw8q62av997wb4KOa7yh_ZgdaL-CfZAh3DSblzALwR6njPAIJhBttMqMOuBmSg'
}

When I check https://login.botframework.com/v1/.well-known/keys, I do not find the key ID ZyGh1GbBL8xd1kOxRYchc1VPSQQ that was in the above authorization header.

This happens whenever I send my bot a message via Teams. For example, if I type "help" when I am in a personal chat with the bot in https://teams.microsoft.com/

I have restarted my server many times to reset the in-process cache that Microsoft's openIdMetadata.js class maintains.

Versions
botbuilder 4.14.1
Node.js 12