Are you using "Em_EEPROM" in your program? What do you see of "went off track in CY8C4126AXI-S433"?
S433 belongs to PSoC4100S family while S455 belongs to PSoC4100S plus, though no much difference.
You'd better share a simple project which can reproduce this issue, then we can analysis the root cause. Seems this two parts have the same FLASH/SRAM size, so this issue should not happen.