The most common cause is grout setting inside the hopper, valves, or delivery hose because washout was delayed or incomplete after use, since cement-based grout can begin hardening within the pump in well under an hour in UAE temperatures. Worn seals or valve seats can also allow grout to bypass and build up in areas not designed for contact. Once set grout hardens inside internal passages, a full strip-down is often required to clear it. Sparkline Group emphasizes immediate post-use washout precisely to prevent this costly failure mode.