Low Earth Orbit (LEO) satellite augmentation is considered a promising solution to enhance Precise Point Positioning (PPP) performance, offering stronger signals and faster geometry changes. Notably, in the absence of a global ground station network tracking LEO navigation signals, LEO-based Positioning, Navigation, and Timing (PNT) applications must depend on orbital and clock products derived from onboard GNSS observations. This operational reliance inherently introduces not only LEO satellite orbital and clock errors, but also hardware biases that distinguish between those of the onboard GNSS receiver contained in the clock estimates and those of the downlinking antenna that are needed by the users. The on-ground calibration of these biases might not cover their in-orbit variations. This study investigates the impacts of these potential LEO-induced errors on LEO-augmented multi-GNSS PPP. Code biases are simulated with different offsets and periodic behaviors for a CentiSpace-like LEO satellite constellation of 150 satellites, and real orbital and clock errors from Sentinel-3B are used to derive the real-time LEO satellite orbital and clock errors used for simulations of the constellation. Using real GNSS observation data from 40 Multi-GNSS Experiment (MGEX) stations and simulated LEO signals considering the above-mentioned errors, the results demonstrated that the convergence time and the positioning accuracy are strongly degraded, sometimes even getting worse than the GNSS-only solutions in case of code biases at the level of tens of ns. These findings underscore the challenges to fully realize the potential of LEO-augmented PPP in real-world applications.