probably, because you have two different VqMod's, with Functions, both accessing the i.E. product.tpl file, in order to replace/add/modify some of the existing content.
When the Server browses trough your VqMod-Section, starting by a and ending by z, it will work itselfs trough the files, without a check, if multiple routines are been done, onto one SOURCE FILE, by multiple VqMod Files or not. So, it possibly produces multiple (end-output-)template-Parts/Sections (in the vqcache-section!). (double/tripple+ -Server-Work!) It then call's 'em, one after one, to finally build the END HTTP OUTPUT File Content out of the Task-MATCHING Ones.. Strictly Alphabethically, according to the Task (the Link called). If no MATCHING VqMod Cache Files exist, or if they are outdated, the Server will create a new SET OF SUCH FILES, as soon as the next Task for this WHATEVER PAGE/PART comes in.
If, by example, two MOD's access the SAME ANCHOR/TAG/WHATEVER (you want to call it) on a Source File, to use it, to add, before, instead of, after, it's own content, or even JUST remove something, the possibillity, that the DEFAULT ANCHOR/TAG/WHATEVER does not longer exist, in exactly this form, after an 'earlier called' VqMod did it's own Job on the Source, is a FACT. Because of this, some VqMod's suddenly produce strange errors, when another seemengly simple VqMod is added to the system.
The only way to fix this, would be, to combine ALL the VqMod Content of VqMod's, ACCESSING THE SAME FILE, like a CATEGORY or PRODUCT PAGE, into one single VqMod. It not only speeds up general Performance, it also makes it easier to modify or change something, without taking the risk to screw up, unaware of the consequences, in another Place, because of this.
Good Luck
Ernie
openshop.li/shop/
PS. My personal understanding of this, it may not be representative!
