I don't know for Render Slave or Hire Out Mercenary.
I remember using the warrior to medium infantry upgrade recently (not sure if it was exactly on the same game).
I'm going to check these and bring more elements if I can (both are on variations of the same game).
Here's what I 've found on the non GP actions.
I started a new game (quick speed), and tried with the slaves policies :
- rendering slaves for gold or for prod give the same Lua error I described before (EaActions.lua:1004: attempt to index upvalue 'g_unit' (a nil value))
And another game where I researched the relevant techs and policies, mined naphta, yew, etc. So :
- I don't have any icon for alternate upgrade catapults --> fire catapults (but the regular catapult --> trebuchet is in and working; the fire catapult can be built in a city and can be upgraded to fire trebuchet)
- trackers can upgrade to rangers. The other upgrade icon is mislabelled: "Increases the apparent size of your civilization and military might by 8%". This label matches what I expect for pyramids (and I remember that in other games the pyramids label was telling something like "placeholder"). If I click it, the tracker is upgraded to bowmen (which is correct)
- rangers can upgrade to heavy infantry or marksmen (and the label is correct). However the marksmanship tech wasn't researched yet. Marksmen cannot be built directly in my cities until the research.
- Bowmen can be upgraded to marksmen after the tech is researched only (without level restriction )
- trebuchets can upgrade to bombards without chemistry
- I can hire out a unit (with the required policy). It was then listed in the additional information mercenery list. On the next turn, the unit disappeared, and I the gold info tells that I'm making 2gold from hired out units.
I know this is complicated, I'll try to explain if you have questions...
Edit: All of this without any Lua error, crash or reloading