I've just gone through a chunk of a bit over 250 research grade observations. Of these, somewhere around 160-175 (around 70%) were males (which are the trickiest to ID and the easiest to misidentify). The accuracy rate was probably around 50%, fairly even among samples of 10 as a whole (incidentally, older IDs were more likely to be accurate while newer IDs were more likely to be inaccurate).

*** I have not yet gone though many female IDs to even speculate an accuracy rate for them. ***

For an idea of where the taxon stands, I see about 600 unreviewd, needs-ID observations. Presuming similar rates, this renders about 420 males with an estimated 210 misidentified males. I'd hypothesize that this is an underestimate as Computer Vision is suggesting this species for any male Myzinum in the US.

Part of the difficulty is that keys require microscopy to be useful and are not all that useful for photography. I've seen a few comments erroneously try to ID specimens from a single trait (generally not a good idea for ID as a whole). I'll link to the key below with the note that only specimens that have already been keyed, through microscopy, to a node regarding wing venation should be run through that node (see further details below).
• https://www.researchgate.net/publication/288606203

Problems with male ID: First, all male M. quinquecinctum have evenly amber-yellow pigmented wings. Hyaline or clear wings immediately rule out this species. However, there seems to be at least one other species with pigmented wings. To be identifiable in photography, the 7th abdominal segment needs to have 2 yellow marks on either side of the pseudostinger. The rarest misidentification I saw had bright red legs (possibly comparable to M. dubiosum) - male M. quinquecinctum should have only yellow-and-black legs. In the absence of this combination of traits, microscopy would be required for species verification.

• Summary of traits: wings evenly amber-yellow pigmented, abdomen T7 with distinct yellow marks

Problems with female ID: Females are less problematic to ID to species, but care still needs to be taken. Typically, the more-frequently observed females can be divided into red-legged and black-legged groups. Black legs rule out M. quinquecinctum but are present in: M. frontalis (highly yellow, unlikely to be mistaken), certain M. maculatum (legs are variable, though), and M. obscurum. This leaves M. carolinanum, M. dubiosum, certain M. maculatum, and M. quinquecinctum as the prevalent red-legged species. The next trait, which is rather unique to M. quinquecinctum, are red antennae (other species have black antennae with scapes colored as follows: yellowish in M. carolinanum; red to black in M. dubiosum; and black in M. maculatum). This combination is typically sufficient for photography, though other traits are useful. Wings in M. quinquecinctum should be evenly pigmented amber-yellow (as with the males). This may leave some M. carolinanum, which seem to range from evenly amber-yellow to lightly bicolored. M. dubiosum are more clear-to-smoky, with any orangish coloration almost being an afterthought, and M. maculatum are strongly bicolored. As an additional note, M. dubiosum typically has fairly restricted abdominal markings.

• Summary of traits: red legs, red antennae, wings evenly amber-yellow pigmented, abdomen with 5 bands (2 and 5 broken)