Genty

I only had to mess with the springs for the Excelsior. When you look at the battery pack you will see that the terminals have a raised plastic lip, if the springs catch on this lip they don't make contact.
I wouldn't risk opening up a ship, not the way they are done now. With the screws being covered you have to remove the covers which would damage them.
With the BOP if you left betteries in it, especially if they were the original ones, I would clean the terminals using something such as white vinegar in a cotton bud (q-tip). A bad battery connection would stop it working. It would help if you had a multimeter in order to check the voltages of the batteries. I would recommend alkaline batteries, zinc one are cheap but leak very easily and can ruin a toy if left in.

I always wondered this about the BoP and Excelsior, if they had a reset button hidden somewhere or not. Are these the only 2 ships released that do not have a reset button on it?

Thankfully (and knock on wood) both of my Klingon BoPs are still working but my NX-2000 decided to sit in spacedock. Changed batteries and flipped the Try Me switch, no lights/no sound

I had a similar problem with one of my Excelsior ships where it didn't work after I changed the batteries. Turns out that the battery sled wasn't making a proper connection when I put it back in. After playing around with the connections a bit I got it working again.
If I remember correctly the inside of the sec hull has springs which connect to the sled, you may just need to stretch them a bit to realign them.

I don't mind some little inaccuracies on a model, it's when there is something that is so wrong that it stands out that bugs me. With the Eaglemoss Ent-C I can live with the lowered nacelles, it's having the wrong sensor dome and lack of impulse engine that I can't stand. Since the pics for the DST one show the right sensor dome I'm happy with it so far. Since it is more than likely just a prototype I'll reserve any more judgement till I see a production onr, probably in 2025.

I wonder if the Enterprise-C will be accurate, the standard one is very inaccurate.

I'm probably being nitpicky but I don't know if it's an optical illusion but Picard's combadge seems a bit low. The other thing is that he has a Boomerang phaser rather than the Cobra. It's a small thing but it's something that would really bug me.
Other than that the sculpts are good, hope to see more pics soon.