Database entries become corrupt - characters shift to next column

[ToneFive]

Greetings all
Firstly, I'm an absolute novice at Access so probably don't have the correct terminology for things. Nevertheless I'll have a go at describing the issue I need help with.
I'm required to use an Access database to track the location of test parts (specimens) and add new specimens to the database. A problem has developed which causes the entries which I create or edit to not appear correctly in the database. After adding a specimen it looks like some characters in the columns become shifted across to the adjacent column and the column titled "Specimen Number" seems to become corrupted. It takes the value 2.42E-308 or 2.38E-308.
This screen capture hopefully shows what I mean. The first 3 entries are corrupt and the following 2 are correct.

I've tried to open the database in the design mode (I do this by holding down the SHIFT button while opening it) and tried to correct the Specimen No values in the first column. When I do this I get a message which says "The search key was not found in any record". The only way to clear this message is to press "ESC", which also makes the specimen number value return to 2.42E-308.
Any ideas what's causing this or how to fix it?
Many thanks

[June7]

Is SpecimenNo field set as number type? Is it Autonumber?

This does seem odd. Have you run Compact & Repair?

If you want to provide db for analysis, follow instructions at bottom of my post.

[ToneFive]

Many thanks June7 for suggesting this. Compact and repair seems to have worked. I've corrected the corrupt entries and so far the database seems to be working correctly.