Schlosser's sign-pattern conjecture for powers of the infinite Borwein product

Let $G_{3}(q)$ be the infinite Borwein product

$$G_{3}(q)=\frac{(q;q)_{\infty}}{(q^{3};q^{3})_{\infty}}.$$

Suppose that $G_{3}(q)^{\delta}$ has the dissection

$$G_{3}(q)^{\delta}=A^{\delta}(q^{3})-qB^{\delta}(q^{3})-q^{2}C^{\delta}(q^{3}).$$

Schlosser's conjecture. If $\delta$ is real and

$$0.227998127341\cdots\approx\frac{9-\sqrt{73}}{2}\leq\delta\leq1\quad\text{or}\quad2\leq\delta\leq3,$$

then $A^{\delta}(q)$, $B^{\delta}(q)$, and $C^{\delta}(q)$ are power series in $q$ with non-negative real coefficients. This extends known sign-regularity phenomena for coefficients of infinite products and their powers; the statement is presented as a conjecture, and no resolution is supplied in the source.