This is very interesting

Shintaro Orihara ADMITS that in Monaco (and on all circuits) the engine generates many problems in all types of corners (although the gearbox does too)
"One of the challenges is to prevent the rear wheels from locking when the driver downshifts during braking. This requires control from the gearbox, and the power unit must correctly supply the engine torque needed for the engine speed to follow the downshift and avoid wheel lockup."
The difficulty lies in the fact that the 2026 model's power unit will use a method of energy generation called partial regeneration more frequently than before.
"When entering a corner, even with the throttle released, the engine generates power almost to the maximum (due to MGU-K braking). If the engine torque fluctuates even slightly, the driver will notice the rear deviating inward during the corner. In Monaco, there's no choice but to drive with a safety margin, so the key is how to stabilize it and enter the corner with the same engine torque, and that's what we're trying to achieve."
This partial regeneration also occurs during acceleration. The internal combustion engine must generate stable engine torque to counteract the braking force of the MGU-K; otherwise, the driver cannot safely press the accelerator. The main cause of this lies in the internal combustion engine's lack of power and its still immature combustion settings.
"Unstable engine torque means unstable combustion. The problem was that the combustion in our internal combustion engine was unstable, causing inconsistent engine torque on each occasion. Up to the Miami GP, we were still looking for a way to solve it, but after the Miami GP, we found a solution that would improve things, and we've been progressively tuning in that direction, so the number of issues we need to resolve has decreased. It has decreased, but we still haven't been able to eliminate them completely, and the big difference is that while on other circuits it's acceptable to stay within this range, in Monaco a much higher level is required (which has made the problems more evident)."
https://x.com/Nachez98/status/2068637864783446210