seen a similar issue (for centrally switched WLANs) with DHCP getting dropped between AP and WLC (apparently by the WLC). Resetting the AP will normally cure it when it establishes a new CAPWAP connection on a new port. We don't seem to have seen it since upgrading to 17.9.4 APSP6....
kaoyn.alTtehrethAeCcEon2-fboramseadtiboinoosernosroierndtaetvioelnopofedthebyligManodre,icroametpraol.m[2is0-] isnhgobwineddianngeesvteimntastetodwliamrditsoaf tdaertgeectt.ioAnc(oLmoDpa)roisfo2n96b0etcwopeieens/omptLic,awl aitnhdaerleescptrooncsheetmimisetroyf alepspsrtohaacnhe3s0ims ...