According to Motorsport Italia it's because of the vibrations.
Translated:
It seemed clear to everyone that it was an empirical solution studied on site, because the two tie-rods were fastened near the single exhaust, to get to the rear diffuser in the hope of "turning off" those annoying resonances that did not allow to exploit the power unit in full potential.
Pierre Gasly made only a few laps with that solution that was then removed, so much so that the French then resumed his work schedule, showing that the Japanese unit has reached a threshold of reliability that was unimaginable last year .
The new 6-cylinder is proving a big step forward compared to 2018 both in terms of reliability and performance, but to get the most out of the potential of the engine it is necessary to "harness" the vibrations that can cause failures not only to the mechanics, but also to the canvas part.
For the sake of completeness of information it is also fair to add that Red Bull replaced the Honda engine as a precautionary measure after Pierre Gasly crashed on Wednesday: the 6-cylinder engine had not broken, but in the end the Japanese preferred to replace it.
