So far the only ones shown that actually breaks continuity is Megatron and Ironhide but there could be excuses while a stretch could be ok. (Unlikely to be true this is just speculation and guessing on my part after waking up in the morning)
For Megatron who says his entire time on Earth before 2007 has been while frozen? We only heard this from Optimus and I think Sector 7 so either of those two could be a little wrong so maybe Megatron roamed around for a little before freezing in the ice during say a search for the Allspark.
Sort of unreleated but how did Sector 7 get Megatron from this...
to this without Megatron unthawing enough for him to kill them all and escape?
As for Ironhide it is never stated that 2007 was his or any of the others first time on Earth while it doesn't exactly make sense for now it's only Ironhide there so perhaps only he arrived on Earth before and then at some point left somehow maybe he met up with Prime, Jazz, and Ratchet and told them about Earth and where it was.
If their bringing Ironhide on Earth early I actually sort of hope they would bring Jazz too since a prequel film could really help him with becoming more of a character.