Paper 1.13.1 latest Shopkeepers version. React shows Shopkeepers is causing a spike. here is timings report

https://timings.aikar.co/?id=c1b203b0fa364c6ba0168286193266f1

I might not interpret the v2 timings correctly, but I don't seem to see the issue to be Shopkeepers..
A few things I can see from the timings:

• In the overworld lots of processing time seems to be spent on entity ticking (mostly guardians), and on chunk generation. Maybe it might make sense to limit the world size and pre-generate all chunks, and look into why there are that many guardians active at the same time.
• In the nether you seem to have lots of pistons active at the same time at some point, which requires Shopkeepers to process lots of BlockPhysicsEvents.

If you are concerneed about the impact of Shopkeeper's BlockPhysicsEvent:
Maybe look into what is causing that many block physics updates (pistons, flowing water/lava, redstone, ..).
Alternatively if this is really an issue: You can disable Shopkeepers reacting to block physics updates by disabling the sign shopkeepers. Maybe disable the sign shopkeepers and see how much that actually impacts your lag issues. You might see a small improvement in the timings, but overall you should still experience situations with lag (assuming everything else stays the same)..

Thanks for the reply. The weird thing is, it worked just fine on 1.12.2 but on 1.13.1 according to react it Shopkeepers spiked 20+ times. I'll disable sign shops and see if that helps

There has been some change inside Spigot to call a few less BlockPhysicsEvents in some situations, requiring Shopkeepers to manually check neighboring blocks for all physics events now. I don't know how big of an impact that is (depends on the types of physics updates being triggered I assume), but overall the checks should still be quite lightweight individually. The biggest issue is still that physics updates can happen quite frequently, especially if you have contraptions involving lots of or constantly running pistons, redstone, flowing water, ..

Closing this as no further information has been provided that might point to a specific issue in Shopkeepers. If you happen to have timings with sign shopkeepers disabled as as comparison, then let me know (out of interest).