SYNTAX ERROR in monitor[48]

This came up in a CITA test (so far I've seen it for the first time, so I'm not too certain wrt reproduceability)

````
"Category": "",
"DM": [
"SYNTAX ERROR",
"monitor[48] done←data[2].{6::0 ⋄ Interval=0}⍬ ⍝ Polling done",
" ∧"
],
"EM": "SYNTAX ERROR",
"EN": 2,
"ENX": 0,
"HelpURL": "",
"InternalLocation": [
"parse.c",
4461
],
"Message": "",
"OSError": [
0,
0,
""
],
"Vendor": "Dyalog"
}
````

BTW, as I looked at the code around that region, I noticed a "80=⎕DR" - shouldn't this by formulated in a "Classic-compatible" way?