I think it is normal for some ICO token to dropping after the sale over.
It is because most of ICO have pre-sale period that have more discount from ICO main sale price.
So, if the token was not locked, the pre-sale investors could sell lower than public sale price.
That's totally not normal, if the ICO is normal atleast the price will remains dormant since the investor still not losing trust to their project so they didnt dump. Instead if a project is just merely over hyped then there will be a mass dumping because the Pre-ICO phase have far cheaper price resulting in mass dumping and investor trying to take a small profit out of this.