Falcon 900
Air Traffic Control Fully Certified
Other / Unknown
ATC Issue All Types
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings
Aircraft X was preceding direct HALIE direct MDW; descending to cross 60 miles East of HALIE at FL240. When Aircraft X was roughly 20 miles West of FWA; I noticed Aircraft X was in coast track; with no altitude read out. There was a Mode C intruder beneath the data block; showing FL296. I asked Aircraft X to report his altitude; and the data block disappeared; I was left with only a Mode C intruder; and the Mode C intruder showed a transponder code one digit off from Aircraft X's code. I tried to start a track; got some ridiculous fail message; I told Aircraft X  to reset his transponder; tried to start a track again; got a ridiculous fail message; coordinated with the two surrounding sectors (LOGAN and BEARZ) and then Aircraft X's data block reappeared. The LOGAN Controller was one of our ERAM SMEs and he said since the (incorrect) code is not recognized; ERAM will not display a data block. I recommend we fall back to HOST immediately. Fortunately; all my attention was directed at Aircraft X while the episode occurred. Had my attention been directed elsewhere; it may have been some time before I recognized I was missing a crucial data block; that I had a Mode C intruder; and the issue needed to be corrected by reassigning Aircraft X the appropriate beacon code. For a data block to randomly drop off is unsafe. Controllers deserve a better system.
ZAU Controller voiced concern regarding an ERAM dropped data block; recommending a return to the HOST RADAR system.