I'm calling for specific canon problems found in GURPS:Traveller books.
Frankly, I don't expect many problems or discrepancies to show up. The reason for this is because Loren is, well, Loren, and because the writers tend to be very knowledgeable about Traveller (what we call "canon").
But, there might be some. If so, please let me know.
Aside from the "GURPS Authors put way too many niggling details in"
BTC wasn't checked against extant canon - it redefines a lot of worlds features
GTGF erroneously states that regiments exist only on paper, and uses the british approach of Battalions directly in Brigades.... which is counter to SMC, 5FW, CT Bk4, MT IE, MT RC, MT RSB, and a handful of T4 sources.
GT preserves the "Loren says all marines are trained in battledress armor" controversy, which is contradictory to CT, MT, and T4 - where only some marines can even wear the stuff; further not all CT imperial marines have vacc suit as a formal skill, and we see Imperial Marines in other armors in multiple sources, which also postdate loren's article, so the assertiion that they wear it as a field uniform are also counter indicated. In MT and T4, all marines are capable of wearing a vacc suit, but lack the requisite skill to don Battledress - which requires either Battledress 0 or Vacc Suit 1. (I cannot tell which way T5 falls on this - T5 CGen still leaves me baffled.)
GT:FT presumes a high trade, low local reliance, model that is counter to MT Hard Times and to T4, and also CT's TTA. TTA shows a much lower number of freighters than should be in port by GT rules - by TWO orders of magnitude. Similarly, other portraits of starport traffic are one to two orders of magnitude lower than GTFT.
GT Nobles pretty much simply needs to be scrapped. It's counter to several T4 sources, doesn't jive with CT/MT nobles articles, doesn't match the later T5 system (which may be Galaxiad, not 3I), introduces new levels of government counter to the CT & MT articles on government... Cluster Counts, for example - CT says flat out that in the imperium, there is no category between individual world governments and subsector governments. Further still, Canon says the Subsector Duke rules a Subsector, not a "duchy"; this is a niggle, but the term Duchy has connotations of control that a Subsector canonically explicitly does not have.
GT's ship designs as a whole are built with different assumptions for power plants than any other edition. Further, the GT ship system is derived from G:V (for GURPS 3rd Revised), and so has numerous minor niggles and disconnects.