rftools-1.12-7.12.jar
I'm just testing a setup. Block protector is protecting only one block, the spawner. The space above the spawner is a 3x3 cube, just enough to spawn in the wither manually.

Once wither spawns, the explosion immediately destroys the spawner, which was supposed to be protected by the block protector. Wither then drops through the hole created by the destroyed spawner. =(

Block protector is powered with a flux point on a flux network with a gargantuan flux storage. I also set the flux point to ignore limit....So power is not an issue. Block protector was also 100% infused.

Inverting the position of the spawner makes no difference

May I suggest a fully infused spawner is simply added to the list of blocks that can resist wither explosions (spawning explosion, black skulls, blue skulls). This will negate the need to use the buggy block protector?

Still occurs in rftools-1.12-7.13.
I've now added a shield layer right below the spawner that is set to activate when the wither is detected to protect the spawner.

I cannot reproduce this: I tried it as follows:

https://i.imgur.com/b5U0QwA.png

So the block protector protects both itself and the powercell and the wither spawned right next to it.

Strange. Maybe something in the pack is messing this up somehow

I don't know. I'll provide a download link with my pack and world with a test setup for you to reproduce.

I downloaded the world from my server and tested in single player. It appears that single player has no issues, only on multiplayer. Server uses spongeforge and not just forge. Outside of you coming on to my server, I don't see how it can be reproduced.

I'm currently using spongeforge-1.12.2-2529-7.0.0-BETA-2732.jar and forge-1.12.2-14.23.0.2529-universal.jar

Here is the pack. It only has the mods I used and the config folder. My server is whitelist only so if you want to come on there let me know.

As an aside, I want to use opencomputer to read the key, bulk, and living matter values in a spawner. Can that be done? I tried putting an adapter next to the spawner, but the spawner didn't seem to show up as a component. There's some complicated matter beaming sequence that I want to try but only do able with a lua program.

I'm on DW20 1.12 pack and am experiencing the same thing. I've used the spawner before on other packs and have never had an issue with the wither destroying the spawner even without the block protector.

Are you playing on server or singleplayer when it happened? The issue only occurs on hosted server for me.

It happens on Single Player on the DW20 1.12, but it doesn't happen at all (even w/o the protector) on the server I play on running 1.12.2. The server is running a friends pack called Gamealition https://www.curseforge.com/minecraft/modpacks/gamealition-pack-a-new-hope

For me it is the complete opposite.

Why did you close this? Is it fixed for you now?

No it is not, but I do not think it is fixable and maybe out of your hand because I use SpongeForge. Besides, I can work around the issue. If you want, you can reopen it. I could also provide a new link for my pack if that will be helpful for you. You would need to test it under multiplayer.

Ah okay, the fact that it's a Sponge issue was what I was missing.

That is my guess, I could be very wrong as I never used anything else other than SpongeForge to host multiplayer server; and since the issue doesn't appear in singleplayer, I reasonably guessed that it is due to how SpongeForge handles ticking.