If a bug is a flaw in the code that will always result in a reproducable error by a certain act, then this is not really bug. It's very annoying nonetheless.

This is the problem:
Ever since we upgraded to 4.3.0 we are experiencing errors that we can't explain.
Two errors are consistent in the fact that they are always the same, but in consistent in the fact that they appear - seemingly - at random.
1. is with an online form. The form consists of 9 pages and i'm using sessions to gather all the data before inserting it into a database. On average 7 people a day fill in this form and on average once every two weeks, there's one person who's data from the first two pages 'gets lost'.

2. i've written a function that will email any 'problem with a query to the database' to me and display an error on the webpage. Since i'm still developping it, i get these emails fairly often. However, sometimes the email is a big garble. I can understand any scepticism towards my programming abilities, but i'll try to make a convincing case by the following illustration:
this is the part were the email is being sent to me:

[php]
mail(
	'me@mail.nl',
	'Error in de Database',
	$body."\n".$getvalues."\n".$postvalues."\n\n".$computer,
	"From: Admin <me@mail.nl>\nReply-To: me@mail.nl");
[/php]

Whatever happens before and after, i hope you agree that IF the email gets send to me, the subject should be 'Error in de Database'. It can't be different. However, in those cases where the body of my email is a garble, the subject contains fragments of what should be stored in the variable $computer.

Also, another very (in my eyes convincing example) is that just 30 minutes ago something strange happened (which triggered me into responding: That Does It!! :)
I've created a message system for registered users. When inserting a message into the database it inserts a timestamp generated by php (i have my reasons for not using the DATETIME type column). The timestamp is created by 
[php]
date(YmdHis)
[/php]
After over 500 correct messages, today one gets inserted as
date(Ymdhis). Instead of 13 it got 01 for hours.

I hope this bug-report is helpfull and if anyone has experienced similar problems, i would appreciate some feedback.