Why does this Googlesheets workbook take so long to update?

[azairvine]

https://docs.google.com/spreadsheets/d/1mrmVxKVgG1JWtIpXi6pca2mck8WJhbFQACsxtCqXCOQ/edit?usp=sharing

I've got a tonne of VLOOKUP references - and maybe the conditional formatting isn't as efficient as it could be (it was the only way I could figure it out).

Everything does what it needs to do, but it can take 10-20min to populate the cells and format the cells colours etc when I enter new data. It's not a big drama as nothing is really time dependant, I'm just interested to know what's causing the bottleneck. From what I've read sheets need to be gargantuan in theory to slow the processing down.

I'm using an i5 with 16GB RAM - the browser (Firefox) doesn't go over 4GB RAM and about 40% CPU while the sheets are updating.

I'm assuming that anyone who loads the workbook will see the lag if they click on the "Pack Opening" tab - it's supposed to look something like this:

 

[azairvine]

The sheet that I linked may not demonstrate the delays I'm experiencing as it's a stripped down template with fewer sheets. The lag seems to be most significant with the cell colours - conditional formatting in other words.