What is a run-through and how do I avoid one in escape from tarkov?
A run through means that you didn't meet the minimum XP threshold for it to count as surviving a raid.
Even though you might spend 20 minutes running around looting, avoiding firefights, getting quest items, if you don't hit the minimum required XP you will miss out on thousands of extra bonus XP.
You can avoid the run through by getting at least 300 XP while you're in the raid. Looting and searching things, healing, eating and drinking, and getting kills will get you XP. Headshots give a bonus XP, also make sure to loot the body of anyone you kill... it gives you extra XP on top of the kill.
Some quests require you to Survive and Extract and a run through doesn't count as surviving... so if you need it for a quest make sure you meet at least the 300 XP minimum.