Client lag on single client (out of 6 total)

Running 6 EvE clients on a single PC and using feeds to control the 5 slaves. Using symlinks so IS is setup to use a different executable for each client, and each client has it's own default profile. This was setup before I was aware of ISBoxer's ability to use a single game install and keep separate settings for each client. My setup works and I can easily find my cache.

Lately, I've noticed lag on a single client; specifically when I'm looting thru that client's feed. At first, it was noticable but not bad. Since the unified inventory fiasco with Inferno expansion, the lag has gotten significantly worse then a little better when CCP patched for performance. I'm talking in the neighboorhood of 1-3 second delay from when I double-click the wreck until the inventory window updates.

Strange thing and why I'm posting this here and not submitting a petition (yet) is that I run 2 Noctis in my fleet and only one is showing this loot lag since CCP's performance patch. Even stranger is that this client shows no loot lag when I use that client directly.

I thought this may have something to with the symlink, so I went and repaired using EvE's tool. No change. I also looked into ISBoxer's file virtualization but couldn't figure out a way to convert from using symlinks to the virtual files and still maintain a separate cache and settings for each client. I'd like to keep the separate cache + settings for each account as I don't fly 6 of the exact same setup. Is this possible using virtualization?

Any ideas on what's causing the lag on my single client? The client in question is in slot 4 [JewWandering]. Paste ID for my current config: Paste ID d8931bcca4

Much thanks go out to +Death and Valerian for their insight.

Based on their suggestions I tried the following.
Swapped characters in slots 4 & 6, 4 being the problem client and 6 being my other looter. Problem character displayed similar bad behaviour (loot lag).
I went a step further and had the problem character use my other looter's profile. Loot lag disappeared. So it's not an IS/ISBoxer problem, but a CCP issue. Not one they're going to fix tho unless it happens repeatedly. Now I need to find a way to migrate my settings, preferably without having to reset this toon. At least my feeds stayed in place

Final update:

My lag problem is fixed. Somehow, the core_user dat file associated with the problem account got hosed. Fix was to copy and rename this file; good file copied from my other looter's settings folder.

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