In Vader.sol, eras are intended to occur every 24 hours. This means that a correct implementation would add 24 hours to the end-time of the previous era in order to find the end-time of the next era. However, the current method for calculating the next eras end-time uses block.timestamp, rather than the previous eras end-time.
This line of code will cause a perpetual drift of era times, causing each era to actually be 24 hours plus the time between when the last era ended and when Vader._transfer() is next called.
Recommend that In Vader.sol, change this:
nextEraTime = block.timestamp + secondsPerEra;
to this:
nextEraTime = nextEraTime + secondsPerEra;
