It is here where Frontios really falls apart for me. Thanks to The Doctor interacting with the Gravis, we get a few more closeups of how silly the head Tractator looks. It's readily apparent that most, if not all, monsters in Doctor Who are men in rubber suits, but it doesn't need to be this obvious. The Gravis has a mouth with teeth, but the mouth never opens, there's no gap between the teeth. Instead, the Gravis's only facial movement is its lower jaw moving in and out in rapid succession.
Also, just how is the TARDIS separated into multiple segments and strewn within the rock in the underground caverns of Frontios? And why is no one surprised by this completely bizarre outcome? The Doctor takes the development in stride, which may explain his indifferent reaction to the TARDIS's supposed destruction at the end of Episode One.
Later, Tegan is separated from The Doctor, Turlough, and Plantaganet for roughly 20 seconds, but that length of time is long enough for the other three to find the TARDIS console room and for Turlough to remember, and relay to the others, the secret of the Tractators. This is the biggest problem with Frontios: everything important seems to happen offscreen. Turlough's explanation of the Gravis and The Doctor's later trip to some uninhabited planet to drop the Gravis off all happen away from our prying eyes, having to be described by other characters afterwards. Television is a visual medium. It's stories should reflect that characteristic.
Frontios is also Paddy Kingsland's last incidental music score for Doctor Who, and it's easily his worst. It's not so much bad as it is incredibly similar and ubiquitous. It's everywhere, often featuring the same pan flute melody. Kingsland, like Frontios, should have been much better than it was.