The Penrite-backed team made a strong start to the Gen3 era, lead driver Reynolds scoring a pole and podium in Newcastle, followed by another podium in Perth.
There were times during the opening three events that the Groves looked to be the strongest of the teams running Ford Mustangs – however there's been a steep decline since.
Both the Tasmania SuperSprint and Darwin Triple Crown were difficult outings, neither Reynolds nor teammate Matt Payne troubling the top 10 across the six collective races.
That's left the team looking for answers, which it hopes it will find during a rookie test for Payne at Winton next week.
The Supercars testing rules give first and second year drivers an additional three days of running, which will allow GR to bank critical running without burning one of its two remaining full test days.
According to Reynolds, the rookie running will be super important heading to Townsville.
"We've got a test day which will be very important," Reynolds told Motorsport.com.
"We need to figure some shit out. It's so close and the cars are very sensitive. They are hard to get into the window and then easy to put outside the window, if you know what I mean.
"Every bit of running you do, especially early on in these new cars, is super critical. We had a few really good test days at the start of the year and we sorted out a lot of stuff and we had a good base. But I think we need to jump to another level."
Reynolds was at a loss to properly explain the Darwin struggles, with the team lacking both pace and luck.
Qualifying speed is one area that needs improvement, while Reynolds wonders if the recent super soft tyre running has shifted the cars outside their set-up window.
"All in all it was a very trying weekend [in Darwin] for both cars. I think out of six races across the two cars, we only finished one of them without having dramas," he said.
"I don't really know what to say. In qualifying we can't get it together.
"I don't know if that's the super soft tyre. The majority of the time on the soft tyre we've been right at the front. Maybe that super soft, we need to make some sort of change for it.
"But yeah, whatever we have doesn't seem to be working. The car doesn't feel as good as it has."
