Category name shows up as "V" on frontpage and in admin products view

[Piszi]

Hello,

There is something strange going on with VirtueMart 2.x and 3.x because in both versions one category name is showing up as "V" instead of its real name in the frontpage and category module and in the admin products view. The actual name is "Sun" but virtuemart is replacing it on the fly. Like if there were an str_replace() or something else.
The minute I put some other char in the name like a dot than it shows up fine.
What could be the problem why is VM replacing the name SUN?
Oh and its a single language store and there are no translations so thats not it.

[Jörgen]

Please give some more information.
http://forum.virtuemart.net/index.php?topic=79799.0

Do You have any extensions installed that could do this, RokCandy or similar ?

regards

Jörgen @ Kreativ Fotografi

[Piszi]

Sorry I left out the technical information.

the live site is a latest J! 2.5 with a very old VM 2.x it has only two non core extensions, one is the Gavick's Image Show GK4 (assigned only to frontpage) and the other is the latest version of CSVI Pro. The template is a custom one made by me, but none of the overrides could affect the category name and it doesn't have any JS functions that could do this.
Also I have one VM core hack in the calculations because I wanted to be able to use percentage instead of price in cusomfields. But this can't affect the category name.
SEF URLs enabled with rewrite (.htaccess)
On the server side: Linux x64, Apache, PHP 5.4.44 (FCGI) and MySQL 5.5.31 with utf8_general_ci Collation

the local site is the latest J! 3.5 with the latest VM 3.x and currently has no extensions except the latest version of CSVI Pro. The template is the J! default Protostar whitout template overrides for VM.
SEF URLs enabled with rewrite (web.config)
On the server side: Windows 10 x64, IIS10, PHP 5.6.16(FCGI) x86, MySQL 5.7.12 x64 with utf8_general_ci Collation/utf8mb4_general_ci Connection Collation

The only similarity between the two site is the CSVI Pro but I think that shouldn't affect the category name at least not on the frontpage or in the category module.

For the live site I created a template override based on the category ID so it currently shows the correct name, but it should show the correct one by default.
Oh and the category in question is a sub category.

Here are some print scrns from the local site:
Admin product categories view: LINK
Admin products view: LINK
Front category view: LINK