Right now, my D-Link DPN-FX3060V (set to bridge mode) is getting capped at 200/50 Mbps after a few days or about a week of use.

I’ve looked through the history threads and found someone shared the firmware, versions v2.0.3 and v2.0.6.

Which version is more stable for bridge mode?

Also, is it safe to update the firmware ourselves? I’m concerned that the update might cause issues like losing network access, or if it might require a technician to reconfigure settings on their end.

Can I know is either version can solve the drop speed issue?

You are assuming too much. There are people on 500meg with rm79 package price.
I'm on 2gig with rm189.
Everything is just a mouse click away.

If he said they just forget to upgrade the speed, just say go ahead and upgrade it as you are promised.

There's no fixed price in TM. In fact there's no standard pricing at all. Everything is arbitrary in TM marketing. I thought people in this forum should know better.