Step to Reproduce:
• place a tile entity e.g. chest, at any negative side of a structure block's bounding box

Observed Results:
At a wall of negative x,y and/or z in a structure block's bounding box, tile entities will not show up in the structure block's preview,
(It will however be able to save them properly)

Expected Results:
Structure block preview would show tile entities located anywhere within their bounding box