  When a topological insulator is incorporated into a Josephson junction, the
system is predicted to reveal the fractional Josephson effect with a
4$\pi$-periodic current-phase relation. Here, we report the measurement of a
$4\pi$-periodic switching current through an asymmetric SQUID, formed by the
higher-order topological insulator WTe$_2$. Contrary to the established
opinion, we show that a high asymmetry in critical current and negligible loop
inductance are not sufficient by themselves to reliably measure the
current-phase relation. Instead, we find that our measurement is heavily
influenced by additional inductances originating from the self-formed
PdTe$_{\text{x}}$ inside the junction. We therefore develop a method to
numerically recover the current-phase relation of the system and find the
$1.5\,\mu \text{m}$ long junction to be best described in the short ballistic
limit. Our results highlight the complexity of subtle inductance effects that
can give rise to misleading topological signatures in transport measurements.
