While on a server, the Light Placer upgrade isnt updating clients that the Miner's Light is there. It only updates when you try to place a block on the Miner's Light, then it updates the client.
This issue is not on Singleplayer

https://streamable.com/29x92o

Interesting, thanks for the report

If it helps, the server has Canary, so that may be influencing things?

I think I've run into this or a similar bug whilst putting together a 1.19.2/Forge 43.2.6 modpack.

As in the OP, client-side is fine. But on a server, mining lights aren't visible until the chunk is unloaded/reloaded or a block update is forced. Also the block breaking/shrinking animation doesn't render; mined blocks just disappear once broken.

I've narrowed down one mod incompatibility: Ad Astra. Removing that mod (v1.12.5) from this mod set solves the light placement/rendering bugs I'm seeing.

Adding a final set of client-side only mods breaks mining gadgets again as above, annoyingly.

Should I file a new bug for all of this or update here if/when I track down the other mod incompatibilitie/s I'm seeing?

This must be a cross mod compatibility problem, because i'm simply calling setblock like I do for most other things :).