Could not book the meeting. unexpected character at line 1 column 1 of the JSON data

[fleabeard69]

Hello,
I'm hosting calcom on a Linode VPS (Ubuntu 22.04 LTS) and trying to book a test meeting but am getting this error Could not book the meeting. unexpected character at line 1 column 1 of the JSON data after a long period of time. I'm using CalDAV with my Nextcloud Calendar. Any ideas why it's failing? I should say that the booking does indeed appear in my "Bookings" tab despite the error.

Here is the last bit of my docker logs -f calcom in hopes it is useful.

@calcom/web:start: sendEmail from: Redacted <redacted@gmail.com> subject: 15 Min Meeting between Redacted and Redacted Error: Connection timeout
@calcom/web:start:     at SMTPConnection._formatError (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:787:19)
@calcom/web:start:     at SMTPConnection._onError (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:773:20)
@calcom/web:start:     at Timeout.<anonymous> (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:232:22)
@calcom/web:start:     at listOnTimeout (node:internal/timers:569:17)
@calcom/web:start:     at process.processTimers (node:internal/timers:512:7) {
@calcom/web:start:   code: 'ETIMEDOUT',
@calcom/web:start:   command: 'CONN'
@calcom/web:start: }
@calcom/web:start: Sendgrid credentials are missing from the .env file
@calcom/web:start: No sendgrid API key provided, returning DUMMY_BATCH_ID
@calcom/web:start: Sendgrid credentials are missing from the .env file
@calcom/web:start: No sendgrid API key provided, skipping email
@calcom/web:start: 16:25:58:667	ERROR[emailReminderManager] Error scheduling email with error PrismaClientKnownRequestError: 
@calcom/web:start: Invalid `prisma.workflowReminder.create()` invocation:
@calcom/web:start: 
@calcom/web:start: 
@calcom/web:start: Unique constraint failed on the fields: (`referenceId`)
@calcom/web:start: [PERF]: getByViewer(1) took 29.594098925590515ms

When canceling the meeting I get this:

UPDATE: I want to make mention that all relevant SMTP/E-Mail ports are open on my VPS.