IMO, Carrhae shows skillful use of catphracts by the Parthians, or, more generally, skilled generalship on Surena's part. It was not always so, though.

In 39 BCE; the Parthians invaded Roman territory, and at the Cilician Gates their cataphracts charged uphill against a Roman camp with predictably disastrous results. One wonders if the Parthians had grown contemptuous of the Romans ater Carrhae. A year later at Gindarus the Parthians charged again straight against another Roman camp. This time, however, an astute Roman general might have fooled them into thinking the camp was undefended. It turned out it wasn't and the Parthian defeat was total, including the killing of a Royal Prince.

Those frontal charges are not that different from what Seleucid cataphracts did at Magnesia. If anything, the Seleucids were somewhat more successful. Antiochos III led 3000 cataphracts and the cavalry Agema (1000) on his right wing in a charge that managed to break one of the four legions opposing him. In Livy's account of the battle it was actually the Latin Ala (not really a Roman legion) in the extreme left of the Roman battle line that Antiochos cavalry outflanked and routed. That would have required the Seleucid cavalry moving diagonally across the whole frontage of both the Roman legion and the Latin Ala (they were not posted in the extreme right as was typical) However, the battle's account in Justin says explicitly that it was the Roman legion right in front the Seleucid cavalry that was routed and that the event was considered a great disgrace, even if the Romans were the eventual victors of the battle. A third account by Appian speaks of the Seleucid king "breaking through the Roman phalanx" which is not very detailed, but seems to agree better with Justin than with Livy. And we know that Livy was not above masking anything that migh reflect poorly on anything Roman....

If we accept Justin's version (which, IMO, given the disposition of the troops and Appian's wording, does not seem unlikely) the Seleucid cataphracts could boast of being one of the very few bodies of ancient cavalry (if not the only) that managed to break a Roman legion by a frontal charge. However, and just to add some more perspective, at the other end of the battlefield another 3000 Seleucid cataphracts were thrown into disorder by fleeing scythed chariots and then Pergamene and Roman cavalry made short work of them.