So I've been playing for a bit, and I've just started to encounter this error with the latest versions of these 2 mods. This wasn't an issue with the latest mods as of October 1st.
It only occurs when a ship in space exploration launches, other than that, there have been no known issues. There is nothing related to Renai on the spaceship itself.
Took it to Space Exploration, and they suggested to take it here. I'm not sure what the protocol is! Renai is very useful for hucking excess waste products into the planet (rocks)

The mod Space Exploration (0.4.47) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event space-exploration::on_tick (ID 0)
The mod Renai Transportation (0.6.4) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event RenaiTransportation::on_entity_cloned (ID 119)
RenaiTransportation/script/event/entity_built.lua:4: attempt to index local 'entity' (a nil value)
stack traceback:
RenaiTransportation/script/event/entity_built.lua:4: in function <RenaiTransportation/script/event/entity_built.lua:1>
stack traceback:
space-exploration/scripts/spaceship.lua:627: in function 'launch'
space-exploration/scripts/spaceship.lua:3341: in function 'stop_integrity_check'
space-exploration/scripts/spaceship.lua:3621: in function 'integrity_check_tick'
space-exploration/scripts/spaceship.lua:2806: in function 'spaceship_tick'
space-exploration/scripts/spaceship.lua:3083: in function 'callback'
space-exploration/scripts/event.lua:15: in function <space-exploration/scripts/event.lua:13>
stack traceback:
[C]: in function 'clone_area'
space-exploration/scripts/spaceship.lua:627: in function 'launch'
space-exploration/scripts/spaceship.lua:3341: in function 'stop_integrity_check'
space-exploration/scripts/spaceship.lua:3621: in function 'integrity_check_tick'
space-exploration/scripts/spaceship.lua:2806: in function 'spaceship_tick'
space-exploration/scripts/spaceship.lua:3083: in function 'callback'
space-exploration/scripts/event.lua:15: in function <space-exploration/scripts/event.lua:13>

I don't know much about space exploration but I'll see what I can find

nvm I know exactly why it's doing that lol, it'll be fixed next version

Thanks!

Try now with 0.6.5, i think it should work, I've never actually played space exploration but it should fix that error

New, possibly related issue with SE:
Failed to load mods:
entity prototype "rail-chain-signal" (rail-chain-signal) collision mask does not collide with entity "RTMagnetTrainRamp-placer" (rail-signal).
rail signal collision masks must collide with all other rail signals.
rail-chain-signal modifications: Base mod › Space Exploration
RTMagnetTrainRamp-placer modifications: Renai Transportation › Space Exploration

Factorio v1.1.1
Space Exploration v0.5.5
Renai v0.6.6

Should be fixed now in 0.6.7, I tried it and it loaded in fine. It's hard to explain but it was just a small tweak SE makes to rail signals that for some reason mess my ramps up. Lemme know if you run into any other problems