Not sure what this error means, or what I might do to give Texis more buffers (if I even can do that). It occured when running a particularly complex query
<!-- 011 [backgroundSearch]:434: Buffer size 0 too small (need 8) for item 479 of page 0x6d400e0 of B-tree (temp RAM DBF) in the function fbtgetnext -->
It's referring to the available space on a fixed-size page in a B-tree; there's no way to increase the buffer size there. The B-tree is essentially saying it backed itself into a corner somehow.
If you're able to reproduce the error with a relatively small and fixed data set, let tech support know.