botframework-sdk: [Direct Line] Bot not responding to user messages. Giving Directline error : "[500] Internal Server Error"

Bot Info

• SDK Platform: NodeJS
• SDK Version: 3.12.0
• Active Channels: Direct Line, Facebook
• Deployment Environment: Manual deployment in VMs of Azure IaaS
• Region of bot deployment: West Europe

Issue Description

Bot suddenly stopped working. It is not responding to user messages randomly. Showing below errors in logs:

Error: Request to 'https://directline.botframework.com/v3/conversations/<some-id>/activities/<some-id>' failed: [500] Internal Server Error
    at Request._callback (/usr/src/app/node_modules/bot-services/node_modules/botbuilder/lib/bots/ChatConnector.js:535:46)
    at Request.self.callback (/usr/src/app/node_modules/bot-services/node_modules/request/request.js:188:22)
    at emitTwo (events.js:106:13)
    at Request.emit (events.js:194:7)
    at Request.<anonymous> (/usr/src/app/node_modules/bot-services/node_modules/request/request.js:1171:10)
    at emitOne (events.js:96:13)
    at Request.emit (events.js:191:7)
    at IncomingMessage.<anonymous> (/usr/src/app/node_modules/bot-services/node_modules/request/request.js:1091:12)
    at Object.onceWrapper (events.js:293:19)
    at emitNone (events.js:91:20)
    at IncomingMessage.emit (events.js:188:7)
    at endReadableNT (_stream_readable.js:975:12)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickDomainCallback (internal/process/next_tick.js:128:9)

Code Example

Reproduction Steps

Expected Behavior

Actual Results