If utilization showing incorrectly for specific interface, one of the reason is speed of the interface may not be correct. Sometimes devices will have bug which shows incorrect speed and other scenario can be ISP provided speed may be different than actual physical speed reported by device and in which case you need to use custom bandwidth, please refer on how to set it Custom Bandwidth/Speed
If poll data points are missing, then the reason could be interface bandwidth is having higher value and if interface consumption is high, counters used to get Rx/Tx bytes may overlap soon. Currently we use SNMP 32 bit counters( ifInOctets 1.3.6.1.2.1.2.2.1.10. , ifOutOctets 1.3.6.1.2.1.2.2.1.16. ) for the same and maximum it can support is 2^32 octets. If the interface speed is having value such as1Gb then these counters will roll over/wrap in short time. Interface utilization uses delta of the current value to previous counters and lead to negative values hence poll data point values gets skipped. Newer device support SNMP 64 bit counters(ifHCInOctets 1.3.6.1.2.1.31.1.1.1.6., ifHCOutOctets 1.3.6.1.2.1.31.1.1.1.10.) which can go up to 2^64 octets and can be configured to use in SapphireIMS provided device support these counters. If for any device which has support for 64 bit counters and has to be added as part of SapphireIMS data collection database/schema, then please reach out to SapphireIMS support for assistance.