I've read about there being range limitations when using TDMA digital modes, like DMR, due to clock drift in the base and mobile stations. The issue seems to be the slot timing verses distance and length of transmissions. See section 10.2.3.1.3 on page 112 in the following link to one of the ESTI DMR standards.
https://www.etsi.org/deliver/etsi_ts/102300_102399/10236101/02.03.01_60/ts_10236101v020301p.pdf
Anybody have any experience with this or did the detailed calculations for their installation? I've seen comments where some have gone to FDMA type modes to avoid this issue.