The Bug:
Totems of undyings don't work if you switch to it too slowly before you die. The more latency you have (or ping) and the more server-lag there is, the bigger the delay.

Steps to Reproduce:

1. Join any server that you get a high latency on (by for example joining a server hosted in North America while you live in any other region outside of it like Europe).
2. Get yourself some obsidian, end crystals and a totem of undying
3. Place an obsidian and an end crystal on it.
4. Switch to your totem of undying and detonate it immediately after.

Expected Behavior:

Switching to totem should be the same for every player to keep things fair.

Actual Behavior:

The delay to switch to totem is different depending on what your latency to your server is, and how much server-lag there is.

The Solution
The server-side waits for the "switch to totem" packet for a specific amount of time + the latency of the player that died. For example the server-side could wait for exactly 30ms + 109ms from the player's latency.

The result? All players regardless of their latency and server-lag will have exactly the same amount of time to switch to totem before they die.

Why This Solution?

The thing with this bug is that there MUST be a delay to switch to totem otherwise people would be invincible. The latency of a player and the server lag will make it unfair for people with high latency. 

The delay of this would be very good at 0.25 seconds for pvp. Why this delay specifically? It's because of d-taps which is a method of quickly killing someone holding a totem with end crystals. A delay of 0.25 seconds will give people 0.25 seconds to react which is close to the average reaction time, again because of d-taps.

Well, what is a d-tap? A d-tap is a technique used in end crystal PvP to quickly kill someone holding a totem of undying. When you hit someone with a sword their body goes red (called a damage tick). You then combine the damage from you sword with 1 end crystal within the same damage tick. After their damage tick ends you crystal them again which will kill them.

Here's a video which explains more about d-taps / 2-taps https://www.youtube.com/watch?v=4LN5Uf7KHW0

Footage

Here's a video of me reproducing the bug (it's not a very good video because that's not the delay that people usually have to deal with since I was the only one online and the server wasn't lagging whatsoever):

https://youtu.be/i_pWiBZj2dY

Here's a video showing how 0.25 or 250ms looks like:

https://youtu.be/hLE6MaVUC0M