This should not be happen vs This should not be happened

Some examples from the web:

• This should not be allowed to happen again.
• I think it is most necessary that we as the European Union say that this should not be allowed to happen in a country that currently holds the chair in the Council of Europe's Committee of Ministers.
• In today's world where everything happens suddenly shows the sign that anything could be happen to anyone.
• But this shouldn't happen tomorrow.
• This should only happen during dist-upgrade or install.
• This should not happen in Europe.
• More common in neaonates and may be happen in young children too
• take out your feelings nothing will be happen with these small accidents
• Things like this shouldn't happen.
• But this should happen without losing democratic accountability in important matters.
• Only the period in which this should happen, needs some modification.
• This should all happen within the framework of a revitalised Euro-Mediterranean dialogue.
• Obviously, this should never have been allowed to happen.
• It is the intention of the presidency that this should happen.
• I think it is absolutely scandalous that this should happen again.
• If this should happen to you, tell your doctor or radiologist.
• 1 timed out. This should not happen.
• An unknown error occurred to %1. This should not happen.
• That this should happen towards the end of our century is not by happenstance.
• Incorrect results are returned and this should not happen.

Some examples from the web:

• This should have happened a long time ago under better circumstances.
• This should've happened lifetimes ago, and...
• You know none of this should ever have happened.
• None of this should have happened.
• Okay? None of this should have happened.
• This should have happened a long time ago under better circumstances.
• I think this should actually have happened months ago - incidentally, the first Commission communication dates from February.
• Now, given the structure of cancer, this should not have happened.
• This should have happened a lot sooner.
• For a bunch of untrained Germanic tribesmen to hem in three legions and basically wipe the whole of them out, this should never have happened.
• But this should also be a time for them to reflect on what happened and why.
• This should have happened earlier, but it is good that there will now be rules.
• This should have never happened, baby. That's not an answer.
• This shouldn't have happened after so many Marcialongas, being here, pushed by others onto the banks of the river. Broken.
• If you remembered that we're friends that have seem that movie eleven times together... then something like this should've never happened.
• It has to be happened and arranged by an Italian institution
• This should normally have happened in his own country, Chile, but apparently this has not been possible because the dictatorships have been maintained.
• I find it so unacceptable that this should have happened that I should personally like to express my disapproval.
• Work happened later, marriage happened later, kids happened later, even death happened later.
• What happened, happened, And...