There is a basic assumption that any REIT yielding above ~5% should have either some elevated idiosyncratic (company specific) risks or with majority of the cash flows stemming from a very cyclical sector. For example, let's have a look on a few examples of REITs, which currently provide above 5% yield.
Source: NAREIT
The list can of course be made much longer, but the main takeaways explaining abnormally high dividends are extreme leverage, secondary/tertiary markets and sector specific macro risks.
However, Global Self Storage (SELF) is somewhat of an outlier. SELF is placed