We describe PTT-MULTITAN, our submission to the WMT26 MT Evaluation shared task, Task 3 (error-free segment detection). The task requires a binary decision — does a machine translation contain any error? — without ac- cess to reference translations, and is scored with the Matthews Correlation Coefficient (MCC). Our system combines a supervised classifier fitted on WMT25 human error-span annotations with three families of reference- free indicators: structural and phraseological cues, corpus-linguistic association measures computed over an LLM-as-judge model, and format/locale conformity checks. We have im- proved our system submissions, whose MCC rises from 0.159 to 0.168. We submitted six language pairs from the official WMT26 test set. The pairs were from English into Belaru- sian, German, Russian, Ukrainian, Simplified Chinese, and Traditional Chinese.