As has been discussed and nicely documented by Rosi, West PP05TT27 shows some instability in the most recent IV scan.  Looking through the complete set, I see four more tiles that may be showing fluctuations, though not nearly as bad.

Tiles with instability:

• West PP05 TT27 - figure 1 -  this is the one we've been focusing on.
• West PP02 TT22 - figure 2
• West PP06 TT27 - figure 3
• West PP10 TT07 - figure 4
• East  PP10 TT17 - figure 5

Some commonalities

• In each case, the unstable tile has higher-than-average dark current (as compared to his neighbors).  Not surprising and almost certainly not a coincidence.
• Two of the five tiles are TT27.  Probably a coincidence.
• Four of the five are on the West side.  If this was caused by a "beam incident," then this might not be coincidental.  But 4/5 can very easily be chance, as well.

Figure 1: West PP05.  Clearly TT27 (in grey) shows instability.  It also has by far the largest dark current.  Note the log scale.  This is the one we've been focusing on.

Figure 2 - West PP02.  Tile 22 (in dark yellow) shows some instability.

Figure 3 - West PP06.  TT27, in dark grey, shows instability, though it is obscured somewhat by the other curves.

Figure 4 - West PP10.  TT07 (bright green) shows clear instability, though it is partially obscured by the other curves.

Figure 5 - East PP10.  TT17 (bright red) shows clear instability, which is partially obscured by the other curves.  TT27 (dark grey) might be a bit unstable as well.