There is a crash in qhandlemanagers_p.h line 146:
Q_ASSERT(m_activeEntryCount < qHandle::MaxIndex);

when creating large number of meshes. The Assert comes from attribute manager. Meshes have one geometry node, but can create multiple attribute nodes. The node managers have book-keeping bits per node manager and if one creates approx. 13k plane meshes, it produces over 65k attributes, which will overflow the book-keeping bits.