A system, comprising: signal acquisition circuitry, which is configured to receive multiple intra-cardiac signals acquired by multiple electrodes of an intra-cardiac probe in a heart of a patient; and a processor, which is configured to: perform a sequence of annotation-visualization operations at subsequent times, by performing, in each operation: (i) extracting multiple annotation values from the intra-cardiac signals; (ii) selecting a group of the intra-cardiac signals, wherein for each subsequent annotation-visualization operation the processor forms the group by, starting with the group formed in the previous annotation-visualization operation, removing some, but not all, of the old values and adding new values, where old and new refer to the sequential number of the cardiac cycle in which a signal was acquired; (iii) identifying in the group one or more annotation values that are statistically deviant by more than a predefined measure of deviation; and (iv) visualizing the annotation values to a user, while omitting and refraining from visualizing the statistically deviant annotation values; assess, over one or more of the annotation-visualization operations, a rate of omission of the annotation values; and take a corrective action in response to detecting that the rate of omissions exceeds a predefined threshold, wherein the processor is configured to take the corrective action by: re-applying the group's omitted annotation values and re-identifying the statistically deviant annotation values. signal acquisition circuitry, which is configured to receive multiple intra-cardiac signals acquired by multiple electrodes of an intra-cardiac probe in a heart of a patient; and a processor, which is configured to: perform a sequence of annotation-visualization operations at subsequent times, by performing, in each operation: (i) extracting multiple annotation values from the intra-cardiac signals; (ii) selecting a group of the intra-cardiac signals, wherein for each subsequent annotation-visualization operation the processor forms the group by, starting with the group formed in the previous annotation-visualization operation, removing some, but not all, of the old values and adding new values, where old and new refer to the sequential number of the cardiac cycle in which a signal was acquired; (iii) identifying in the group one or more annotation values that are statistically deviant by more than a predefined measure of deviation; and (iv) visualizing the annotation values to a user, while omitting and refraining from visualizing the statistically deviant annotation values; assess, over one or more of the annotation-visualization operations, a rate of omission of the annotation values; and take a corrective action in response to detecting that the rate of omissions exceeds a predefined threshold, wherein the processor is configured to take the corrective action by: re-applying the group's omitted annotation values and re-identifying the statistically deviant annotation values. perform a sequence of annotation-visualization operations at subsequent times, by performing, in each operation: (i) extracting multiple annotation values from the intra-cardiac signals; (ii) selecting a group of the intra-cardiac signals, wherein for each subsequent annotation-visualization operation the processor forms the group by, starting with the group formed in the previous annotation-visualization operation, removing some, but not all, of the old values and adding new values, where old and new refer to the sequential number of the cardiac cycle in which a signal was acquired; (iii) identifying in the group one or more annotation values that are statistically deviant by more than a predefined measure of deviation; and (iv) visualizing the annotation values to a user, while omitting and refraining from visualizing the statistically deviant annotation values; (i) extracting multiple annotation values from the intra-cardiac signals; (ii) selecting a group of the intra-cardiac signals, wherein for each subsequent annotation-visualization operation the processor forms the group by, starting with the group formed in the previous annotation-visualization operation, removing some, but not all, of the old values and adding new values, where old and new refer to the sequential number of the cardiac cycle in which a signal was acquired; (iii) identifying in the group one or more annotation values that are statistically deviant by more than a predefined measure of deviation; and (iv) visualizing the annotation values to a user, while omitting and refraining from visualizing the statistically deviant annotation values; assess, over one or more of the annotation-visualization operations, a rate of omission of the annotation values; and take a corrective action in response to detecting that the rate of omissions exceeds a predefined threshold, wherein the processor is configured to take the corrective action by: re-applying the group's omitted annotation values and re-identifying the statistically deviant annotation values.