When one sleeps in the tropics, it simply progresses to the middle of the night in that dimension

I'm not using Sponge, as it breaks several of the mods I use.

Could not duplicate this on my server. Set time to 8:00pm, placed bed, went to sleep, woke up at 6:00am with sun coming up.

forge-1.12.2-14.23.2.2611
SpongeForge 7.1.0-BETA-2990
Tropicraft 7.1.3.62

You sure someone didn't simply get out of bed in the middle of the night?

One player is in the overworld while I'm in the tropics.

I do have morpheus installed, however.

I've had trouble with Morpheus, in many ways. When it comes to dimensions, it's dev believes it's on dimension mod devs to support Morpheus, rather than Morpheus simply doing server-wide sleep or working per-dimension.
I would suggest SleepVote for Sponge if you are running Sponge. If Forge only...can't help ya.

Take Morpheus out of the equation and see if it still happens. I would bet it doesn't, and I highly recommend finding something else to handle sleep.

This is the sort of thing I'm referring to. No dimension mod should have to add support for a sleep mod, for the sleep mod to behave properly in this case.

Can confirm, time does not advance while sleeping in the tropics dim.
Single player, no morpheus, no sponge.
forge-1.12.2-14.23.5.2768
tropicraft-MC1.12.2-7.1.8.105